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	<li><a class="reference internal" href="#">Transports and Protocols</a><ul>
	<li><a class="reference internal" href="#transports">Transports</a><ul>
	<li><a class="reference internal" href="#transports-hierarchy">Transports Hierarchy</a></li>
	<li><a class="reference internal" href="#base-transport">Base Transport</a></li>
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	<li><a class="reference internal" href="#write-only-transports">Write-only Transports</a></li>
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	<li><a class="reference internal" href="#loop-subprocess-exec-and-subprocessprotocol">loop.subprocess_exec() and SubprocessProtocol</a></li>
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	<section id="transports-and-protocols">
	<span id="asyncio-transports-protocols"></span><h1>Transports and Protocols<a class="headerlink" href="#transports-and-protocols" title="Link to this heading">¶</a></h1>
	<p class="rubric">Preface</p>
	<p>Transports and Protocols are used by the <strong>low-level</strong> event loop
	APIs such as <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.create_connection" title="asyncio.loop.create_connection"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.create_connection()</span></code></a>. They use
	callback-based programming style and enable high-performance
	implementations of network or IPC protocols (e.g. HTTP).</p>
	<p>Essentially, transports and protocols should only be used in
	libraries and frameworks and never in high-level asyncio
	applications.</p>
	<p>This documentation page covers both <a class="reference internal" href="#transports">Transports</a> and <a class="reference internal" href="#protocols">Protocols</a>.</p>
	<p class="rubric">Introduction</p>
	<p>At the highest level, the transport is concerned with <em>how</em> bytes
	are transmitted, while the protocol determines <em>which</em> bytes to
	transmit (and to some extent when).</p>
	<p>A different way of saying the same thing: a transport is an
	abstraction for a socket (or similar I/O endpoint) while a protocol
	is an abstraction for an application, from the transport’s point
	of view.</p>
	<p>Yet another view is the transport and protocol interfaces
	together define an abstract interface for using network I/O and
	interprocess I/O.</p>
	<p>There is always a 1:1 relationship between transport and protocol
	objects: the protocol calls transport methods to send data,
	while the transport calls protocol methods to pass it data that
	has been received.</p>
	<p>Most of connection oriented event loop methods
	(such as <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.create_connection" title="asyncio.loop.create_connection"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.create_connection()</span></code></a>) usually accept a
	<em>protocol_factory</em> argument used to create a <em>Protocol</em> object
	for an accepted connection, represented by a <em>Transport</em> object.
	Such methods usually return a tuple of <code class="docutils literal notranslate"><span class="pre">(transport,</span> <span class="pre">protocol)</span></code>.</p>
	<p class="rubric">Contents</p>
	<p>This documentation page contains the following sections:</p>
	<ul class="simple">
	<li><p>The <a class="reference internal" href="#transports">Transports</a> section documents asyncio <a class="reference internal" href="#asyncio.BaseTransport" title="asyncio.BaseTransport"><code class="xref py py-class docutils literal notranslate"><span class="pre">BaseTransport</span></code></a>,
	<a class="reference internal" href="#asyncio.ReadTransport" title="asyncio.ReadTransport"><code class="xref py py-class docutils literal notranslate"><span class="pre">ReadTransport</span></code></a>, <a class="reference internal" href="#asyncio.WriteTransport" title="asyncio.WriteTransport"><code class="xref py py-class docutils literal notranslate"><span class="pre">WriteTransport</span></code></a>, <a class="reference internal" href="#asyncio.Transport" title="asyncio.Transport"><code class="xref py py-class docutils literal notranslate"><span class="pre">Transport</span></code></a>,
	<a class="reference internal" href="#asyncio.DatagramTransport" title="asyncio.DatagramTransport"><code class="xref py py-class docutils literal notranslate"><span class="pre">DatagramTransport</span></code></a>, and <a class="reference internal" href="#asyncio.SubprocessTransport" title="asyncio.SubprocessTransport"><code class="xref py py-class docutils literal notranslate"><span class="pre">SubprocessTransport</span></code></a>
	classes.</p></li>
	<li><p>The <a class="reference internal" href="#protocols">Protocols</a> section documents asyncio <a class="reference internal" href="#asyncio.BaseProtocol" title="asyncio.BaseProtocol"><code class="xref py py-class docutils literal notranslate"><span class="pre">BaseProtocol</span></code></a>,
	<a class="reference internal" href="#asyncio.Protocol" title="asyncio.Protocol"><code class="xref py py-class docutils literal notranslate"><span class="pre">Protocol</span></code></a>, <a class="reference internal" href="#asyncio.BufferedProtocol" title="asyncio.BufferedProtocol"><code class="xref py py-class docutils literal notranslate"><span class="pre">BufferedProtocol</span></code></a>,
	<a class="reference internal" href="#asyncio.DatagramProtocol" title="asyncio.DatagramProtocol"><code class="xref py py-class docutils literal notranslate"><span class="pre">DatagramProtocol</span></code></a>, and <a class="reference internal" href="#asyncio.SubprocessProtocol" title="asyncio.SubprocessProtocol"><code class="xref py py-class docutils literal notranslate"><span class="pre">SubprocessProtocol</span></code></a> classes.</p></li>
	<li><p>The <a class="reference internal" href="#examples">Examples</a> section showcases how to work with transports,
	protocols, and low-level event loop APIs.</p></li>
	</ul>
	<section id="transports">
	<span id="asyncio-transport"></span><h2>Transports<a class="headerlink" href="#transports" title="Link to this heading">¶</a></h2>
	<p><strong>Source code:</strong> <a class="extlink-source reference external" href="https://github.com/python/cpython/tree/main/Lib/asyncio/transports.py">Lib/asyncio/transports.py</a></p>
	<hr class="docutils" />
	<p>Transports are classes provided by <a class="reference internal" href="asyncio.html#module-asyncio" title="asyncio: Asynchronous I/O."><code class="xref py py-mod docutils literal notranslate"><span class="pre">asyncio</span></code></a> in order to abstract
	various kinds of communication channels.</p>
	<p>Transport objects are always instantiated by an
	<a class="reference internal" href="asyncio-eventloop.html#asyncio-event-loop"><span class="std std-ref">asyncio event loop</span></a>.</p>
	<p>asyncio implements transports for TCP, UDP, SSL, and subprocess pipes.
	The methods available on a transport depend on the transport’s kind.</p>
	<p>The transport classes are <a class="reference internal" href="asyncio-dev.html#asyncio-multithreading"><span class="std std-ref">not thread safe</span></a>.</p>
	<section id="transports-hierarchy">
	<h3>Transports Hierarchy<a class="headerlink" href="#transports-hierarchy" title="Link to this heading">¶</a></h3>
	<dl class="py class">
	<dt class="sig sig-object py" id="asyncio.BaseTransport">
	<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">asyncio.</span></span><span class="sig-name descname"><span class="pre">BaseTransport</span></span><a class="headerlink" href="#asyncio.BaseTransport" title="Link to this definition">¶</a></dt>
	<dd><p>Base class for all transports. Contains methods that all
	asyncio transports share.</p>
	</dd></dl>

	<dl class="py class">
	<dt class="sig sig-object py" id="asyncio.WriteTransport">
	<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">asyncio.</span></span><span class="sig-name descname"><span class="pre">WriteTransport</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">BaseTransport</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.WriteTransport" title="Link to this definition">¶</a></dt>
	<dd><p>A base transport for write-only connections.</p>
	<p>Instances of the <em>WriteTransport</em> class are returned from
	the <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.connect_write_pipe" title="asyncio.loop.connect_write_pipe"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.connect_write_pipe()</span></code></a> event loop method and
	are also used by subprocess-related methods like
	<a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.subprocess_exec" title="asyncio.loop.subprocess_exec"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.subprocess_exec()</span></code></a>.</p>
	</dd></dl>

	<dl class="py class">
	<dt class="sig sig-object py" id="asyncio.ReadTransport">
	<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">asyncio.</span></span><span class="sig-name descname"><span class="pre">ReadTransport</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">BaseTransport</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.ReadTransport" title="Link to this definition">¶</a></dt>
	<dd><p>A base transport for read-only connections.</p>
	<p>Instances of the <em>ReadTransport</em> class are returned from
	the <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.connect_read_pipe" title="asyncio.loop.connect_read_pipe"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.connect_read_pipe()</span></code></a> event loop method and
	are also used by subprocess-related methods like
	<a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.subprocess_exec" title="asyncio.loop.subprocess_exec"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.subprocess_exec()</span></code></a>.</p>
	</dd></dl>

	<dl class="py class">
	<dt class="sig sig-object py" id="asyncio.Transport">
	<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">asyncio.</span></span><span class="sig-name descname"><span class="pre">Transport</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">WriteTransport</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">ReadTransport</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.Transport" title="Link to this definition">¶</a></dt>
	<dd><p>Interface representing a bidirectional transport, such as a
	TCP connection.</p>
	<p>The user does not instantiate a transport directly; they call a
	utility function, passing it a protocol factory and other
	information necessary to create the transport and protocol.</p>
	<p>Instances of the <em>Transport</em> class are returned from or used by
	event loop methods like <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.create_connection" title="asyncio.loop.create_connection"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.create_connection()</span></code></a>,
	<a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.create_unix_connection" title="asyncio.loop.create_unix_connection"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.create_unix_connection()</span></code></a>,
	<a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.create_server" title="asyncio.loop.create_server"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.create_server()</span></code></a>, <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.sendfile" title="asyncio.loop.sendfile"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.sendfile()</span></code></a>, etc.</p>
	</dd></dl>

	<dl class="py class">
	<dt class="sig sig-object py" id="asyncio.DatagramTransport">
	<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">asyncio.</span></span><span class="sig-name descname"><span class="pre">DatagramTransport</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">BaseTransport</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.DatagramTransport" title="Link to this definition">¶</a></dt>
	<dd><p>A transport for datagram (UDP) connections.</p>
	<p>Instances of the <em>DatagramTransport</em> class are returned from
	the <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.create_datagram_endpoint" title="asyncio.loop.create_datagram_endpoint"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.create_datagram_endpoint()</span></code></a> event loop method.</p>
	</dd></dl>

	<dl class="py class">
	<dt class="sig sig-object py" id="asyncio.SubprocessTransport">
	<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">asyncio.</span></span><span class="sig-name descname"><span class="pre">SubprocessTransport</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">BaseTransport</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.SubprocessTransport" title="Link to this definition">¶</a></dt>
	<dd><p>An abstraction to represent a connection between a parent and its
	child OS process.</p>
	<p>Instances of the <em>SubprocessTransport</em> class are returned from
	event loop methods <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.subprocess_shell" title="asyncio.loop.subprocess_shell"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.subprocess_shell()</span></code></a> and
	<a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.subprocess_exec" title="asyncio.loop.subprocess_exec"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.subprocess_exec()</span></code></a>.</p>
	</dd></dl>

	</section>
	<section id="base-transport">
	<h3>Base Transport<a class="headerlink" href="#base-transport" title="Link to this heading">¶</a></h3>
	<dl class="py method">
	<dt class="sig sig-object py" id="asyncio.BaseTransport.close">
	<span class="sig-prename descclassname"><span class="pre">BaseTransport.</span></span><span class="sig-name descname"><span class="pre">close</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.BaseTransport.close" title="Link to this definition">¶</a></dt>
	<dd><p>Close the transport.</p>
	<p>If the transport has a buffer for outgoing
	data, buffered data will be flushed asynchronously. No more data
	will be received. After all buffered data is flushed, the
	protocol’s <a class="reference internal" href="#asyncio.BaseProtocol.connection_lost" title="asyncio.BaseProtocol.connection_lost"><code class="xref py py-meth docutils literal notranslate"><span class="pre">protocol.connection_lost()</span></code></a> method will be called with
	<a class="reference internal" href="constants.html#None" title="None"><code class="xref py py-const docutils literal notranslate"><span class="pre">None</span></code></a> as its argument. The transport should not be
	used once it is closed.</p>
	</dd></dl>

	<dl class="py method">
	<dt class="sig sig-object py" id="asyncio.BaseTransport.is_closing">
	<span class="sig-prename descclassname"><span class="pre">BaseTransport.</span></span><span class="sig-name descname"><span class="pre">is_closing</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.BaseTransport.is_closing" title="Link to this definition">¶</a></dt>
	<dd><p>Return <code class="docutils literal notranslate"><span class="pre">True</span></code> if the transport is closing or is closed.</p>
	</dd></dl>

	<dl class="py method">
	<dt class="sig sig-object py" id="asyncio.BaseTransport.get_extra_info">
	<span class="sig-prename descclassname"><span class="pre">BaseTransport.</span></span><span class="sig-name descname"><span class="pre">get_extra_info</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">name</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">default</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.BaseTransport.get_extra_info" title="Link to this definition">¶</a></dt>
	<dd><p>Return information about the transport or underlying resources
	it uses.</p>
	<p><em>name</em> is a string representing the piece of transport-specific
	information to get.</p>
	<p><em>default</em> is the value to return if the information is not
	available, or if the transport does not support querying it
	with the given third-party event loop implementation or on the
	current platform.</p>
	<p>For example, the following code attempts to get the underlying
	socket object of the transport:</p>
	<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">sock</span> <span class="o">=</span> <span class="n">transport</span><span class="o">.</span><span class="n">get_extra_info</span><span class="p">(</span><span class="s1">'socket'</span><span class="p">)</span>
	<span class="k">if</span> <span class="n">sock</span> <span class="ow">is</span> <span class="ow">not</span> <span class="kc">None</span><span class="p">:</span>
	<span class="nb">print</span><span class="p">(</span><span class="n">sock</span><span class="o">.</span><span class="n">getsockopt</span><span class="p">(</span><span class="o">...</span><span class="p">))</span>
	</pre></div>
	</div>
	<p>Categories of information that can be queried on some transports:</p>
	<ul class="simple">
	<li><p>socket:</p>
	<ul>
	<li><p><code class="docutils literal notranslate"><span class="pre">'peername'</span></code>: the remote address to which the socket is
	connected, result of <a class="reference internal" href="socket.html#socket.socket.getpeername" title="socket.socket.getpeername"><code class="xref py py-meth docutils literal notranslate"><span class="pre">socket.socket.getpeername()</span></code></a>
	(<code class="docutils literal notranslate"><span class="pre">None</span></code> on error)</p></li>
	<li><p><code class="docutils literal notranslate"><span class="pre">'socket'</span></code>: <a class="reference internal" href="socket.html#socket.socket" title="socket.socket"><code class="xref py py-class docutils literal notranslate"><span class="pre">socket.socket</span></code></a> instance</p></li>
	<li><p><code class="docutils literal notranslate"><span class="pre">'sockname'</span></code>: the socket’s own address,
	result of <a class="reference internal" href="socket.html#socket.socket.getsockname" title="socket.socket.getsockname"><code class="xref py py-meth docutils literal notranslate"><span class="pre">socket.socket.getsockname()</span></code></a></p></li>
	</ul>
	</li>
	<li><p>SSL socket:</p>
	<ul>
	<li><p><code class="docutils literal notranslate"><span class="pre">'compression'</span></code>: the compression algorithm being used as a
	string, or <code class="docutils literal notranslate"><span class="pre">None</span></code> if the connection isn’t compressed; result
	of <a class="reference internal" href="ssl.html#ssl.SSLSocket.compression" title="ssl.SSLSocket.compression"><code class="xref py py-meth docutils literal notranslate"><span class="pre">ssl.SSLSocket.compression()</span></code></a></p></li>
	<li><p><code class="docutils literal notranslate"><span class="pre">'cipher'</span></code>: a three-value tuple containing the name of the
	cipher being used, the version of the SSL protocol that defines
	its use, and the number of secret bits being used; result of
	<a class="reference internal" href="ssl.html#ssl.SSLSocket.cipher" title="ssl.SSLSocket.cipher"><code class="xref py py-meth docutils literal notranslate"><span class="pre">ssl.SSLSocket.cipher()</span></code></a></p></li>
	<li><p><code class="docutils literal notranslate"><span class="pre">'peercert'</span></code>: peer certificate; result of
	<a class="reference internal" href="ssl.html#ssl.SSLSocket.getpeercert" title="ssl.SSLSocket.getpeercert"><code class="xref py py-meth docutils literal notranslate"><span class="pre">ssl.SSLSocket.getpeercert()</span></code></a></p></li>
	<li><p><code class="docutils literal notranslate"><span class="pre">'sslcontext'</span></code>: <a class="reference internal" href="ssl.html#ssl.SSLContext" title="ssl.SSLContext"><code class="xref py py-class docutils literal notranslate"><span class="pre">ssl.SSLContext</span></code></a> instance</p></li>
	<li><p><code class="docutils literal notranslate"><span class="pre">'ssl_object'</span></code>: <a class="reference internal" href="ssl.html#ssl.SSLObject" title="ssl.SSLObject"><code class="xref py py-class docutils literal notranslate"><span class="pre">ssl.SSLObject</span></code></a> or
	<a class="reference internal" href="ssl.html#ssl.SSLSocket" title="ssl.SSLSocket"><code class="xref py py-class docutils literal notranslate"><span class="pre">ssl.SSLSocket</span></code></a> instance</p></li>
	</ul>
	</li>
	<li><p>pipe:</p>
	<ul>
	<li><p><code class="docutils literal notranslate"><span class="pre">'pipe'</span></code>: pipe object</p></li>
	</ul>
	</li>
	<li><p>subprocess:</p>
	<ul>
	<li><p><code class="docutils literal notranslate"><span class="pre">'subprocess'</span></code>: <a class="reference internal" href="subprocess.html#subprocess.Popen" title="subprocess.Popen"><code class="xref py py-class docutils literal notranslate"><span class="pre">subprocess.Popen</span></code></a> instance</p></li>
	</ul>
	</li>
	</ul>
	</dd></dl>

	<dl class="py method">
	<dt class="sig sig-object py" id="asyncio.BaseTransport.set_protocol">
	<span class="sig-prename descclassname"><span class="pre">BaseTransport.</span></span><span class="sig-name descname"><span class="pre">set_protocol</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">protocol</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.BaseTransport.set_protocol" title="Link to this definition">¶</a></dt>
	<dd><p>Set a new protocol.</p>
	<p>Switching protocol should only be done when both
	protocols are documented to support the switch.</p>
	</dd></dl>

	<dl class="py method">
	<dt class="sig sig-object py" id="asyncio.BaseTransport.get_protocol">
	<span class="sig-prename descclassname"><span class="pre">BaseTransport.</span></span><span class="sig-name descname"><span class="pre">get_protocol</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.BaseTransport.get_protocol" title="Link to this definition">¶</a></dt>
	<dd><p>Return the current protocol.</p>
	</dd></dl>

	</section>
	<section id="read-only-transports">
	<h3>Read-only Transports<a class="headerlink" href="#read-only-transports" title="Link to this heading">¶</a></h3>
	<dl class="py method">
	<dt class="sig sig-object py" id="asyncio.ReadTransport.is_reading">
	<span class="sig-prename descclassname"><span class="pre">ReadTransport.</span></span><span class="sig-name descname"><span class="pre">is_reading</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.ReadTransport.is_reading" title="Link to this definition">¶</a></dt>
	<dd><p>Return <code class="docutils literal notranslate"><span class="pre">True</span></code> if the transport is receiving new data.</p>
	<div class="versionadded">
	<p><span class="versionmodified added">Added in version 3.7.</span></p>
	</div>
	</dd></dl>

	<dl class="py method">
	<dt class="sig sig-object py" id="asyncio.ReadTransport.pause_reading">
	<span class="sig-prename descclassname"><span class="pre">ReadTransport.</span></span><span class="sig-name descname"><span class="pre">pause_reading</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.ReadTransport.pause_reading" title="Link to this definition">¶</a></dt>
	<dd><p>Pause the receiving end of the transport. No data will be passed to
	the protocol’s <a class="reference internal" href="#asyncio.Protocol.data_received" title="asyncio.Protocol.data_received"><code class="xref py py-meth docutils literal notranslate"><span class="pre">protocol.data_received()</span></code></a>
	method until <a class="reference internal" href="#asyncio.ReadTransport.resume_reading" title="asyncio.ReadTransport.resume_reading"><code class="xref py py-meth docutils literal notranslate"><span class="pre">resume_reading()</span></code></a> is called.</p>
	<div class="versionchanged">
	<p><span class="versionmodified changed">Changed in version 3.7: </span>The method is idempotent, i.e. it can be called when the
	transport is already paused or closed.</p>
	</div>
	</dd></dl>

	<dl class="py method">
	<dt class="sig sig-object py" id="asyncio.ReadTransport.resume_reading">
	<span class="sig-prename descclassname"><span class="pre">ReadTransport.</span></span><span class="sig-name descname"><span class="pre">resume_reading</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.ReadTransport.resume_reading" title="Link to this definition">¶</a></dt>
	<dd><p>Resume the receiving end. The protocol’s
	<a class="reference internal" href="#asyncio.Protocol.data_received" title="asyncio.Protocol.data_received"><code class="xref py py-meth docutils literal notranslate"><span class="pre">protocol.data_received()</span></code></a> method
	will be called once again if some data is available for reading.</p>
	<div class="versionchanged">
	<p><span class="versionmodified changed">Changed in version 3.7: </span>The method is idempotent, i.e. it can be called when the
	transport is already reading.</p>
	</div>
	</dd></dl>

	</section>
	<section id="write-only-transports">
	<h3>Write-only Transports<a class="headerlink" href="#write-only-transports" title="Link to this heading">¶</a></h3>
	<dl class="py method">
	<dt class="sig sig-object py" id="asyncio.WriteTransport.abort">
	<span class="sig-prename descclassname"><span class="pre">WriteTransport.</span></span><span class="sig-name descname"><span class="pre">abort</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.WriteTransport.abort" title="Link to this definition">¶</a></dt>
	<dd><p>Close the transport immediately, without waiting for pending operations
	to complete. Buffered data will be lost. No more data will be received.
	The protocol’s <a class="reference internal" href="#asyncio.BaseProtocol.connection_lost" title="asyncio.BaseProtocol.connection_lost"><code class="xref py py-meth docutils literal notranslate"><span class="pre">protocol.connection_lost()</span></code></a> method will eventually be
	called with <a class="reference internal" href="constants.html#None" title="None"><code class="xref py py-const docutils literal notranslate"><span class="pre">None</span></code></a> as its argument.</p>
	</dd></dl>

	<dl class="py method">
	<dt class="sig sig-object py" id="asyncio.WriteTransport.can_write_eof">
	<span class="sig-prename descclassname"><span class="pre">WriteTransport.</span></span><span class="sig-name descname"><span class="pre">can_write_eof</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.WriteTransport.can_write_eof" title="Link to this definition">¶</a></dt>
	<dd><p>Return <a class="reference internal" href="constants.html#True" title="True"><code class="xref py py-const docutils literal notranslate"><span class="pre">True</span></code></a> if the transport supports
	<a class="reference internal" href="#asyncio.WriteTransport.write_eof" title="asyncio.WriteTransport.write_eof"><code class="xref py py-meth docutils literal notranslate"><span class="pre">write_eof()</span></code></a>, <a class="reference internal" href="constants.html#False" title="False"><code class="xref py py-const docutils literal notranslate"><span class="pre">False</span></code></a> if not.</p>
	</dd></dl>

	<dl class="py method">
	<dt class="sig sig-object py" id="asyncio.WriteTransport.get_write_buffer_size">
	<span class="sig-prename descclassname"><span class="pre">WriteTransport.</span></span><span class="sig-name descname"><span class="pre">get_write_buffer_size</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.WriteTransport.get_write_buffer_size" title="Link to this definition">¶</a></dt>
	<dd><p>Return the current size of the output buffer used by the transport.</p>
	</dd></dl>

	<dl class="py method">
	<dt class="sig sig-object py" id="asyncio.WriteTransport.get_write_buffer_limits">
	<span class="sig-prename descclassname"><span class="pre">WriteTransport.</span></span><span class="sig-name descname"><span class="pre">get_write_buffer_limits</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.WriteTransport.get_write_buffer_limits" title="Link to this definition">¶</a></dt>
	<dd><p>Get the <em>high</em> and <em>low</em> watermarks for write flow control. Return a
	tuple <code class="docutils literal notranslate"><span class="pre">(low,</span> <span class="pre">high)</span></code> where <em>low</em> and <em>high</em> are positive number of
	bytes.</p>
	<p>Use <a class="reference internal" href="#asyncio.WriteTransport.set_write_buffer_limits" title="asyncio.WriteTransport.set_write_buffer_limits"><code class="xref py py-meth docutils literal notranslate"><span class="pre">set_write_buffer_limits()</span></code></a> to set the limits.</p>
	<div class="versionadded">
	<p><span class="versionmodified added">Added in version 3.4.2.</span></p>
	</div>
	</dd></dl>

	<dl class="py method">
	<dt class="sig sig-object py" id="asyncio.WriteTransport.set_write_buffer_limits">
	<span class="sig-prename descclassname"><span class="pre">WriteTransport.</span></span><span class="sig-name descname"><span class="pre">set_write_buffer_limits</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">high</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">low</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.WriteTransport.set_write_buffer_limits" title="Link to this definition">¶</a></dt>
	<dd><p>Set the <em>high</em> and <em>low</em> watermarks for write flow control.</p>
	<p>These two values (measured in number of
	bytes) control when the protocol’s
	<a class="reference internal" href="#asyncio.BaseProtocol.pause_writing" title="asyncio.BaseProtocol.pause_writing"><code class="xref py py-meth docutils literal notranslate"><span class="pre">protocol.pause_writing()</span></code></a>
	and <a class="reference internal" href="#asyncio.BaseProtocol.resume_writing" title="asyncio.BaseProtocol.resume_writing"><code class="xref py py-meth docutils literal notranslate"><span class="pre">protocol.resume_writing()</span></code></a>
	methods are called. If specified, the low watermark must be less
	than or equal to the high watermark. Neither <em>high</em> nor <em>low</em>
	can be negative.</p>
	<p><a class="reference internal" href="#asyncio.BaseProtocol.pause_writing" title="asyncio.BaseProtocol.pause_writing"><code class="xref py py-meth docutils literal notranslate"><span class="pre">pause_writing()</span></code></a> is called when the buffer size
	becomes greater than or equal to the <em>high</em> value. If writing has
	been paused, <a class="reference internal" href="#asyncio.BaseProtocol.resume_writing" title="asyncio.BaseProtocol.resume_writing"><code class="xref py py-meth docutils literal notranslate"><span class="pre">resume_writing()</span></code></a> is called when
	the buffer size becomes less than or equal to the <em>low</em> value.</p>
	<p>The defaults are implementation-specific. If only the
	high watermark is given, the low watermark defaults to an
	implementation-specific value less than or equal to the
	high watermark. Setting <em>high</em> to zero forces <em>low</em> to zero as
	well, and causes <a class="reference internal" href="#asyncio.BaseProtocol.pause_writing" title="asyncio.BaseProtocol.pause_writing"><code class="xref py py-meth docutils literal notranslate"><span class="pre">pause_writing()</span></code></a> to be called
	whenever the buffer becomes non-empty. Setting <em>low</em> to zero causes
	<a class="reference internal" href="#asyncio.BaseProtocol.resume_writing" title="asyncio.BaseProtocol.resume_writing"><code class="xref py py-meth docutils literal notranslate"><span class="pre">resume_writing()</span></code></a> to be called only once the
	buffer is empty. Use of zero for either limit is generally
	sub-optimal as it reduces opportunities for doing I/O and
	computation concurrently.</p>
	<p>Use <a class="reference internal" href="#asyncio.WriteTransport.get_write_buffer_limits" title="asyncio.WriteTransport.get_write_buffer_limits"><code class="xref py py-meth docutils literal notranslate"><span class="pre">get_write_buffer_limits()</span></code></a>
	to get the limits.</p>
	</dd></dl>

	<dl class="py method">
	<dt class="sig sig-object py" id="asyncio.WriteTransport.write">
	<span class="sig-prename descclassname"><span class="pre">WriteTransport.</span></span><span class="sig-name descname"><span class="pre">write</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">data</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.WriteTransport.write" title="Link to this definition">¶</a></dt>
	<dd><p>Write some <em>data</em> bytes to the transport.</p>
	<p>This method does not block; it buffers the data and arranges for it
	to be sent out asynchronously.</p>
	</dd></dl>

	<dl class="py method">
	<dt class="sig sig-object py" id="asyncio.WriteTransport.writelines">
	<span class="sig-prename descclassname"><span class="pre">WriteTransport.</span></span><span class="sig-name descname"><span class="pre">writelines</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">list_of_data</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.WriteTransport.writelines" title="Link to this definition">¶</a></dt>
	<dd><p>Write a list (or any iterable) of data bytes to the transport.
	This is functionally equivalent to calling <a class="reference internal" href="#asyncio.WriteTransport.write" title="asyncio.WriteTransport.write"><code class="xref py py-meth docutils literal notranslate"><span class="pre">write()</span></code></a> on each
	element yielded by the iterable, but may be implemented more
	efficiently.</p>
	</dd></dl>

	<dl class="py method">
	<dt class="sig sig-object py" id="asyncio.WriteTransport.write_eof">
	<span class="sig-prename descclassname"><span class="pre">WriteTransport.</span></span><span class="sig-name descname"><span class="pre">write_eof</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.WriteTransport.write_eof" title="Link to this definition">¶</a></dt>
	<dd><p>Close the write end of the transport after flushing all buffered data.
	Data may still be received.</p>
	<p>This method can raise <a class="reference internal" href="exceptions.html#NotImplementedError" title="NotImplementedError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">NotImplementedError</span></code></a> if the transport
	(e.g. SSL) doesn’t support half-closed connections.</p>
	</dd></dl>

	</section>
	<section id="datagram-transports">
	<h3>Datagram Transports<a class="headerlink" href="#datagram-transports" title="Link to this heading">¶</a></h3>
	<dl class="py method">
	<dt class="sig sig-object py" id="asyncio.DatagramTransport.sendto">
	<span class="sig-prename descclassname"><span class="pre">DatagramTransport.</span></span><span class="sig-name descname"><span class="pre">sendto</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">data</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">addr</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.DatagramTransport.sendto" title="Link to this definition">¶</a></dt>
	<dd><p>Send the <em>data</em> bytes to the remote peer given by <em>addr</em> (a
	transport-dependent target address). If <em>addr</em> is <a class="reference internal" href="constants.html#None" title="None"><code class="xref py py-const docutils literal notranslate"><span class="pre">None</span></code></a>,
	the data is sent to the target address given on transport
	creation.</p>
	<p>This method does not block; it buffers the data and arranges
	for it to be sent out asynchronously.</p>
	<div class="versionchanged">
	<p><span class="versionmodified changed">Changed in version 3.13: </span>This method can be called with an empty bytes object to send a
	zero-length datagram. The buffer size calculation used for flow
	control is also updated to account for the datagram header.</p>
	</div>
	</dd></dl>

	<dl class="py method">
	<dt class="sig sig-object py" id="asyncio.DatagramTransport.abort">
	<span class="sig-prename descclassname"><span class="pre">DatagramTransport.</span></span><span class="sig-name descname"><span class="pre">abort</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.DatagramTransport.abort" title="Link to this definition">¶</a></dt>
	<dd><p>Close the transport immediately, without waiting for pending
	operations to complete. Buffered data will be lost.
	No more data will be received. The protocol’s
	<a class="reference internal" href="#asyncio.BaseProtocol.connection_lost" title="asyncio.BaseProtocol.connection_lost"><code class="xref py py-meth docutils literal notranslate"><span class="pre">protocol.connection_lost()</span></code></a>
	method will eventually be called with <a class="reference internal" href="constants.html#None" title="None"><code class="xref py py-const docutils literal notranslate"><span class="pre">None</span></code></a> as its argument.</p>
	</dd></dl>

	</section>
	<section id="subprocess-transports">
	<span id="asyncio-subprocess-transports"></span><h3>Subprocess Transports<a class="headerlink" href="#subprocess-transports" title="Link to this heading">¶</a></h3>
	<dl class="py method">
	<dt class="sig sig-object py" id="asyncio.SubprocessTransport.get_pid">
	<span class="sig-prename descclassname"><span class="pre">SubprocessTransport.</span></span><span class="sig-name descname"><span class="pre">get_pid</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.SubprocessTransport.get_pid" title="Link to this definition">¶</a></dt>
	<dd><p>Return the subprocess process id as an integer.</p>
	</dd></dl>

	<dl class="py method">
	<dt class="sig sig-object py" id="asyncio.SubprocessTransport.get_pipe_transport">
	<span class="sig-prename descclassname"><span class="pre">SubprocessTransport.</span></span><span class="sig-name descname"><span class="pre">get_pipe_transport</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">fd</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.SubprocessTransport.get_pipe_transport" title="Link to this definition">¶</a></dt>
	<dd><p>Return the transport for the communication pipe corresponding to the
	integer file descriptor <em>fd</em>:</p>
	<ul class="simple">
	<li><p><code class="docutils literal notranslate"><span class="pre">0</span></code>: writable streaming transport of the standard input (<em>stdin</em>),
	or <a class="reference internal" href="constants.html#None" title="None"><code class="xref py py-const docutils literal notranslate"><span class="pre">None</span></code></a> if the subprocess was not created with <code class="docutils literal notranslate"><span class="pre">stdin=PIPE</span></code></p></li>
	<li><p><code class="docutils literal notranslate"><span class="pre">1</span></code>: readable streaming transport of the standard output (<em>stdout</em>),
	or <a class="reference internal" href="constants.html#None" title="None"><code class="xref py py-const docutils literal notranslate"><span class="pre">None</span></code></a> if the subprocess was not created with <code class="docutils literal notranslate"><span class="pre">stdout=PIPE</span></code></p></li>
	<li><p><code class="docutils literal notranslate"><span class="pre">2</span></code>: readable streaming transport of the standard error (<em>stderr</em>),
	or <a class="reference internal" href="constants.html#None" title="None"><code class="xref py py-const docutils literal notranslate"><span class="pre">None</span></code></a> if the subprocess was not created with <code class="docutils literal notranslate"><span class="pre">stderr=PIPE</span></code></p></li>
	<li><p>other <em>fd</em>: <a class="reference internal" href="constants.html#None" title="None"><code class="xref py py-const docutils literal notranslate"><span class="pre">None</span></code></a></p></li>
	</ul>
	</dd></dl>

	<dl class="py method">
	<dt class="sig sig-object py" id="asyncio.SubprocessTransport.get_returncode">
	<span class="sig-prename descclassname"><span class="pre">SubprocessTransport.</span></span><span class="sig-name descname"><span class="pre">get_returncode</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.SubprocessTransport.get_returncode" title="Link to this definition">¶</a></dt>
	<dd><p>Return the subprocess return code as an integer or <a class="reference internal" href="constants.html#None" title="None"><code class="xref py py-const docutils literal notranslate"><span class="pre">None</span></code></a>
	if it hasn’t returned, which is similar to the
	<a class="reference internal" href="subprocess.html#subprocess.Popen.returncode" title="subprocess.Popen.returncode"><code class="xref py py-attr docutils literal notranslate"><span class="pre">subprocess.Popen.returncode</span></code></a> attribute.</p>
	</dd></dl>

	<dl class="py method">
	<dt class="sig sig-object py" id="asyncio.SubprocessTransport.kill">
	<span class="sig-prename descclassname"><span class="pre">SubprocessTransport.</span></span><span class="sig-name descname"><span class="pre">kill</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.SubprocessTransport.kill" title="Link to this definition">¶</a></dt>
	<dd><p>Kill the subprocess.</p>
	<p>On POSIX systems, the function sends SIGKILL to the subprocess.
	On Windows, this method is an alias for <a class="reference internal" href="#asyncio.SubprocessTransport.terminate" title="asyncio.SubprocessTransport.terminate"><code class="xref py py-meth docutils literal notranslate"><span class="pre">terminate()</span></code></a>.</p>
	<p>See also <a class="reference internal" href="subprocess.html#subprocess.Popen.kill" title="subprocess.Popen.kill"><code class="xref py py-meth docutils literal notranslate"><span class="pre">subprocess.Popen.kill()</span></code></a>.</p>
	</dd></dl>

	<dl class="py method">
	<dt class="sig sig-object py" id="asyncio.SubprocessTransport.send_signal">
	<span class="sig-prename descclassname"><span class="pre">SubprocessTransport.</span></span><span class="sig-name descname"><span class="pre">send_signal</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">signal</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.SubprocessTransport.send_signal" title="Link to this definition">¶</a></dt>
	<dd><p>Send the <em>signal</em> number to the subprocess, as in
	<a class="reference internal" href="subprocess.html#subprocess.Popen.send_signal" title="subprocess.Popen.send_signal"><code class="xref py py-meth docutils literal notranslate"><span class="pre">subprocess.Popen.send_signal()</span></code></a>.</p>
	</dd></dl>

	<dl class="py method">
	<dt class="sig sig-object py" id="asyncio.SubprocessTransport.terminate">
	<span class="sig-prename descclassname"><span class="pre">SubprocessTransport.</span></span><span class="sig-name descname"><span class="pre">terminate</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.SubprocessTransport.terminate" title="Link to this definition">¶</a></dt>
	<dd><p>Stop the subprocess.</p>
	<p>On POSIX systems, this method sends <a class="reference internal" href="signal.html#signal.SIGTERM" title="signal.SIGTERM"><code class="xref py py-const docutils literal notranslate"><span class="pre">SIGTERM</span></code></a> to the subprocess.
	On Windows, the Windows API function <code class="xref c c-func docutils literal notranslate"><span class="pre">TerminateProcess()</span></code> is called to
	stop the subprocess.</p>
	<p>See also <a class="reference internal" href="subprocess.html#subprocess.Popen.terminate" title="subprocess.Popen.terminate"><code class="xref py py-meth docutils literal notranslate"><span class="pre">subprocess.Popen.terminate()</span></code></a>.</p>
	</dd></dl>

	<dl class="py method">
	<dt class="sig sig-object py" id="asyncio.SubprocessTransport.close">
	<span class="sig-prename descclassname"><span class="pre">SubprocessTransport.</span></span><span class="sig-name descname"><span class="pre">close</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.SubprocessTransport.close" title="Link to this definition">¶</a></dt>
	<dd><p>Kill the subprocess by calling the <a class="reference internal" href="#asyncio.SubprocessTransport.kill" title="asyncio.SubprocessTransport.kill"><code class="xref py py-meth docutils literal notranslate"><span class="pre">kill()</span></code></a> method.</p>
	<p>If the subprocess hasn’t returned yet, and close transports of
	<em>stdin</em>, <em>stdout</em>, and <em>stderr</em> pipes.</p>
	</dd></dl>

	</section>
	</section>
	<section id="protocols">
	<span id="asyncio-protocol"></span><h2>Protocols<a class="headerlink" href="#protocols" title="Link to this heading">¶</a></h2>
	<p><strong>Source code:</strong> <a class="extlink-source reference external" href="https://github.com/python/cpython/tree/main/Lib/asyncio/protocols.py">Lib/asyncio/protocols.py</a></p>
	<hr class="docutils" />
	<p>asyncio provides a set of abstract base classes that should be used
	to implement network protocols. Those classes are meant to be used
	together with <a class="reference internal" href="#asyncio-transport"><span class="std std-ref">transports</span></a>.</p>
	<p>Subclasses of abstract base protocol classes may implement some or
	all methods. All these methods are callbacks: they are called by
	transports on certain events, for example when some data is received.
	A base protocol method should be called by the corresponding transport.</p>
	<section id="base-protocols">
	<h3>Base Protocols<a class="headerlink" href="#base-protocols" title="Link to this heading">¶</a></h3>
	<dl class="py class">
	<dt class="sig sig-object py" id="asyncio.BaseProtocol">
	<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">asyncio.</span></span><span class="sig-name descname"><span class="pre">BaseProtocol</span></span><a class="headerlink" href="#asyncio.BaseProtocol" title="Link to this definition">¶</a></dt>
	<dd><p>Base protocol with methods that all protocols share.</p>
	</dd></dl>

	<dl class="py class">
	<dt class="sig sig-object py" id="asyncio.Protocol">
	<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">asyncio.</span></span><span class="sig-name descname"><span class="pre">Protocol</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">BaseProtocol</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.Protocol" title="Link to this definition">¶</a></dt>
	<dd><p>The base class for implementing streaming protocols
	(TCP, Unix sockets, etc).</p>
	</dd></dl>

	<dl class="py class">
	<dt class="sig sig-object py" id="asyncio.BufferedProtocol">
	<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">asyncio.</span></span><span class="sig-name descname"><span class="pre">BufferedProtocol</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">BaseProtocol</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.BufferedProtocol" title="Link to this definition">¶</a></dt>
	<dd><p>A base class for implementing streaming protocols with manual
	control of the receive buffer.</p>
	</dd></dl>

	<dl class="py class">
	<dt class="sig sig-object py" id="asyncio.DatagramProtocol">
	<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">asyncio.</span></span><span class="sig-name descname"><span class="pre">DatagramProtocol</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">BaseProtocol</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.DatagramProtocol" title="Link to this definition">¶</a></dt>
	<dd><p>The base class for implementing datagram (UDP) protocols.</p>
	</dd></dl>

	<dl class="py class">
	<dt class="sig sig-object py" id="asyncio.SubprocessProtocol">
	<em class="property"><span class="k"><span class="pre">class</span></span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">asyncio.</span></span><span class="sig-name descname"><span class="pre">SubprocessProtocol</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">BaseProtocol</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.SubprocessProtocol" title="Link to this definition">¶</a></dt>
	<dd><p>The base class for implementing protocols communicating with child
	processes (unidirectional pipes).</p>
	</dd></dl>

	</section>
	<section id="base-protocol">
	<h3>Base Protocol<a class="headerlink" href="#base-protocol" title="Link to this heading">¶</a></h3>
	<p>All asyncio protocols can implement Base Protocol callbacks.</p>
	<p class="rubric">Connection Callbacks</p>
	<p>Connection callbacks are called on all protocols, exactly once per
	a successful connection. All other protocol callbacks can only be
	called between those two methods.</p>
	<dl class="py method">
	<dt class="sig sig-object py" id="asyncio.BaseProtocol.connection_made">
	<span class="sig-prename descclassname"><span class="pre">BaseProtocol.</span></span><span class="sig-name descname"><span class="pre">connection_made</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">transport</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.BaseProtocol.connection_made" title="Link to this definition">¶</a></dt>
	<dd><p>Called when a connection is made.</p>
	<p>The <em>transport</em> argument is the transport representing the
	connection. The protocol is responsible for storing the reference
	to its transport.</p>
	</dd></dl>

	<dl class="py method">
	<dt class="sig sig-object py" id="asyncio.BaseProtocol.connection_lost">
	<span class="sig-prename descclassname"><span class="pre">BaseProtocol.</span></span><span class="sig-name descname"><span class="pre">connection_lost</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">exc</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.BaseProtocol.connection_lost" title="Link to this definition">¶</a></dt>
	<dd><p>Called when the connection is lost or closed.</p>
	<p>The argument is either an exception object or <a class="reference internal" href="constants.html#None" title="None"><code class="xref py py-const docutils literal notranslate"><span class="pre">None</span></code></a>.
	The latter means a regular EOF is received, or the connection was
	aborted or closed by this side of the connection.</p>
	</dd></dl>

	<p class="rubric">Flow Control Callbacks</p>
	<p>Flow control callbacks can be called by transports to pause or
	resume writing performed by the protocol.</p>
	<p>See the documentation of the <a class="reference internal" href="#asyncio.WriteTransport.set_write_buffer_limits" title="asyncio.WriteTransport.set_write_buffer_limits"><code class="xref py py-meth docutils literal notranslate"><span class="pre">set_write_buffer_limits()</span></code></a>
	method for more details.</p>
	<dl class="py method">
	<dt class="sig sig-object py" id="asyncio.BaseProtocol.pause_writing">
	<span class="sig-prename descclassname"><span class="pre">BaseProtocol.</span></span><span class="sig-name descname"><span class="pre">pause_writing</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.BaseProtocol.pause_writing" title="Link to this definition">¶</a></dt>
	<dd><p>Called when the transport’s buffer goes over the high watermark.</p>
	</dd></dl>

	<dl class="py method">
	<dt class="sig sig-object py" id="asyncio.BaseProtocol.resume_writing">
	<span class="sig-prename descclassname"><span class="pre">BaseProtocol.</span></span><span class="sig-name descname"><span class="pre">resume_writing</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.BaseProtocol.resume_writing" title="Link to this definition">¶</a></dt>
	<dd><p>Called when the transport’s buffer drains below the low watermark.</p>
	</dd></dl>

	<p>If the buffer size equals the high watermark,
	<a class="reference internal" href="#asyncio.BaseProtocol.pause_writing" title="asyncio.BaseProtocol.pause_writing"><code class="xref py py-meth docutils literal notranslate"><span class="pre">pause_writing()</span></code></a> is not called: the buffer size must
	go strictly over.</p>
	<p>Conversely, <a class="reference internal" href="#asyncio.BaseProtocol.resume_writing" title="asyncio.BaseProtocol.resume_writing"><code class="xref py py-meth docutils literal notranslate"><span class="pre">resume_writing()</span></code></a> is called when the
	buffer size is equal or lower than the low watermark. These end
	conditions are important to ensure that things go as expected when
	either mark is zero.</p>
	</section>
	<section id="streaming-protocols">
	<h3>Streaming Protocols<a class="headerlink" href="#streaming-protocols" title="Link to this heading">¶</a></h3>
	<p>Event methods, such as <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.create_server" title="asyncio.loop.create_server"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.create_server()</span></code></a>,
	<a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.create_unix_server" title="asyncio.loop.create_unix_server"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.create_unix_server()</span></code></a>, <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.create_connection" title="asyncio.loop.create_connection"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.create_connection()</span></code></a>,
	<a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.create_unix_connection" title="asyncio.loop.create_unix_connection"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.create_unix_connection()</span></code></a>, <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.connect_accepted_socket" title="asyncio.loop.connect_accepted_socket"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.connect_accepted_socket()</span></code></a>,
	<a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.connect_read_pipe" title="asyncio.loop.connect_read_pipe"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.connect_read_pipe()</span></code></a>, and <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.connect_write_pipe" title="asyncio.loop.connect_write_pipe"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.connect_write_pipe()</span></code></a>
	accept factories that return streaming protocols.</p>
	<dl class="py method">
	<dt class="sig sig-object py" id="asyncio.Protocol.data_received">
	<span class="sig-prename descclassname"><span class="pre">Protocol.</span></span><span class="sig-name descname"><span class="pre">data_received</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">data</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.Protocol.data_received" title="Link to this definition">¶</a></dt>
	<dd><p>Called when some data is received. <em>data</em> is a non-empty bytes
	object containing the incoming data.</p>
	<p>Whether the data is buffered, chunked or reassembled depends on
	the transport. In general, you shouldn’t rely on specific semantics
	and instead make your parsing generic and flexible. However,
	data is always received in the correct order.</p>
	<p>The method can be called an arbitrary number of times while
	a connection is open.</p>
	<p>However, <a class="reference internal" href="#asyncio.Protocol.eof_received" title="asyncio.Protocol.eof_received"><code class="xref py py-meth docutils literal notranslate"><span class="pre">protocol.eof_received()</span></code></a>
	is called at most once. Once <code class="docutils literal notranslate"><span class="pre">eof_received()</span></code> is called,
	<code class="docutils literal notranslate"><span class="pre">data_received()</span></code> is not called anymore.</p>
	</dd></dl>

	<dl class="py method">
	<dt class="sig sig-object py" id="asyncio.Protocol.eof_received">
	<span class="sig-prename descclassname"><span class="pre">Protocol.</span></span><span class="sig-name descname"><span class="pre">eof_received</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.Protocol.eof_received" title="Link to this definition">¶</a></dt>
	<dd><p>Called when the other end signals it won’t send any more data
	(for example by calling <a class="reference internal" href="#asyncio.WriteTransport.write_eof" title="asyncio.WriteTransport.write_eof"><code class="xref py py-meth docutils literal notranslate"><span class="pre">transport.write_eof()</span></code></a>, if the other end also uses
	asyncio).</p>
	<p>This method may return a false value (including <code class="docutils literal notranslate"><span class="pre">None</span></code>), in which case
	the transport will close itself. Conversely, if this method returns a
	true value, the protocol used determines whether to close the transport.
	Since the default implementation returns <code class="docutils literal notranslate"><span class="pre">None</span></code>, it implicitly closes the
	connection.</p>
	<p>Some transports, including SSL, don’t support half-closed connections,
	in which case returning true from this method will result in the connection
	being closed.</p>
	</dd></dl>

	<p>State machine:</p>
	<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>start -> connection_made
	[-> data_received]*
	[-> eof_received]?
	-> connection_lost -> end
	</pre></div>
	</div>
	</section>
	<section id="buffered-streaming-protocols">
	<h3>Buffered Streaming Protocols<a class="headerlink" href="#buffered-streaming-protocols" title="Link to this heading">¶</a></h3>
	<div class="versionadded">
	<p><span class="versionmodified added">Added in version 3.7.</span></p>
	</div>
	<p>Buffered Protocols can be used with any event loop method
	that supports <a class="reference internal" href="#streaming-protocols">Streaming Protocols</a>.</p>
	<p><code class="docutils literal notranslate"><span class="pre">BufferedProtocol</span></code> implementations allow explicit manual allocation
	and control of the receive buffer. Event loops can then use the buffer
	provided by the protocol to avoid unnecessary data copies. This
	can result in noticeable performance improvement for protocols that
	receive big amounts of data. Sophisticated protocol implementations
	can significantly reduce the number of buffer allocations.</p>
	<p>The following callbacks are called on <a class="reference internal" href="#asyncio.BufferedProtocol" title="asyncio.BufferedProtocol"><code class="xref py py-class docutils literal notranslate"><span class="pre">BufferedProtocol</span></code></a>
	instances:</p>
	<dl class="py method">
	<dt class="sig sig-object py" id="asyncio.BufferedProtocol.get_buffer">
	<span class="sig-prename descclassname"><span class="pre">BufferedProtocol.</span></span><span class="sig-name descname"><span class="pre">get_buffer</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">sizehint</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.BufferedProtocol.get_buffer" title="Link to this definition">¶</a></dt>
	<dd><p>Called to allocate a new receive buffer.</p>
	<p><em>sizehint</em> is the recommended minimum size for the returned
	buffer. It is acceptable to return smaller or larger buffers
	than what <em>sizehint</em> suggests. When set to -1, the buffer size
	can be arbitrary. It is an error to return a buffer with a zero size.</p>
	<p><code class="docutils literal notranslate"><span class="pre">get_buffer()</span></code> must return an object implementing the
	<a class="reference internal" href="../c-api/buffer.html#bufferobjects"><span class="std std-ref">buffer protocol</span></a>.</p>
	</dd></dl>

	<dl class="py method">
	<dt class="sig sig-object py" id="asyncio.BufferedProtocol.buffer_updated">
	<span class="sig-prename descclassname"><span class="pre">BufferedProtocol.</span></span><span class="sig-name descname"><span class="pre">buffer_updated</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">nbytes</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.BufferedProtocol.buffer_updated" title="Link to this definition">¶</a></dt>
	<dd><p>Called when the buffer was updated with the received data.</p>
	<p><em>nbytes</em> is the total number of bytes that were written to the buffer.</p>
	</dd></dl>

	<dl class="py method">
	<dt class="sig sig-object py" id="asyncio.BufferedProtocol.eof_received">
	<span class="sig-prename descclassname"><span class="pre">BufferedProtocol.</span></span><span class="sig-name descname"><span class="pre">eof_received</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.BufferedProtocol.eof_received" title="Link to this definition">¶</a></dt>
	<dd><p>See the documentation of the <a class="reference internal" href="#asyncio.Protocol.eof_received" title="asyncio.Protocol.eof_received"><code class="xref py py-meth docutils literal notranslate"><span class="pre">protocol.eof_received()</span></code></a> method.</p>
	</dd></dl>

	<p><a class="reference internal" href="#asyncio.BufferedProtocol.get_buffer" title="asyncio.BufferedProtocol.get_buffer"><code class="xref py py-meth docutils literal notranslate"><span class="pre">get_buffer()</span></code></a> can be called an arbitrary number
	of times during a connection. However, <a class="reference internal" href="#asyncio.Protocol.eof_received" title="asyncio.Protocol.eof_received"><code class="xref py py-meth docutils literal notranslate"><span class="pre">protocol.eof_received()</span></code></a> is called at most once
	and, if called, <code class="xref py py-meth docutils literal notranslate"><span class="pre">get_buffer()</span></code> and
	<a class="reference internal" href="#asyncio.BufferedProtocol.buffer_updated" title="asyncio.BufferedProtocol.buffer_updated"><code class="xref py py-meth docutils literal notranslate"><span class="pre">buffer_updated()</span></code></a> won’t be called after it.</p>
	<p>State machine:</p>
	<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>start -> connection_made
	[-> get_buffer
	[-> buffer_updated]?
	]*
	[-> eof_received]?
	-> connection_lost -> end
	</pre></div>
	</div>
	</section>
	<section id="datagram-protocols">
	<h3>Datagram Protocols<a class="headerlink" href="#datagram-protocols" title="Link to this heading">¶</a></h3>
	<p>Datagram Protocol instances should be constructed by protocol
	factories passed to the <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.create_datagram_endpoint" title="asyncio.loop.create_datagram_endpoint"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.create_datagram_endpoint()</span></code></a> method.</p>
	<dl class="py method">
	<dt class="sig sig-object py" id="asyncio.DatagramProtocol.datagram_received">
	<span class="sig-prename descclassname"><span class="pre">DatagramProtocol.</span></span><span class="sig-name descname"><span class="pre">datagram_received</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">data</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">addr</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.DatagramProtocol.datagram_received" title="Link to this definition">¶</a></dt>
	<dd><p>Called when a datagram is received. <em>data</em> is a bytes object containing
	the incoming data. <em>addr</em> is the address of the peer sending the data;
	the exact format depends on the transport.</p>
	</dd></dl>

	<dl class="py method">
	<dt class="sig sig-object py" id="asyncio.DatagramProtocol.error_received">
	<span class="sig-prename descclassname"><span class="pre">DatagramProtocol.</span></span><span class="sig-name descname"><span class="pre">error_received</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">exc</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.DatagramProtocol.error_received" title="Link to this definition">¶</a></dt>
	<dd><p>Called when a previous send or receive operation raises an
	<a class="reference internal" href="exceptions.html#OSError" title="OSError"><code class="xref py py-class docutils literal notranslate"><span class="pre">OSError</span></code></a>. <em>exc</em> is the <code class="xref py py-class docutils literal notranslate"><span class="pre">OSError</span></code> instance.</p>
	<p>This method is called in rare conditions, when the transport (e.g. UDP)
	detects that a datagram could not be delivered to its recipient.
	In many conditions though, undeliverable datagrams will be silently
	dropped.</p>
	</dd></dl>

	<div class="admonition note">
	<p class="admonition-title">Note</p>
	<p>On BSD systems (macOS, FreeBSD, etc.) flow control is not supported
	for datagram protocols, because there is no reliable way to detect send
	failures caused by writing too many packets.</p>
	<p>The socket always appears ‘ready’ and excess packets are dropped. An
	<a class="reference internal" href="exceptions.html#OSError" title="OSError"><code class="xref py py-class docutils literal notranslate"><span class="pre">OSError</span></code></a> with <code class="docutils literal notranslate"><span class="pre">errno</span></code> set to <a class="reference internal" href="errno.html#errno.ENOBUFS" title="errno.ENOBUFS"><code class="xref py py-const docutils literal notranslate"><span class="pre">errno.ENOBUFS</span></code></a> may
	or may not be raised; if it is raised, it will be reported to
	<a class="reference internal" href="#asyncio.DatagramProtocol.error_received" title="asyncio.DatagramProtocol.error_received"><code class="xref py py-meth docutils literal notranslate"><span class="pre">DatagramProtocol.error_received()</span></code></a> but otherwise ignored.</p>
	</div>
	</section>
	<section id="subprocess-protocols">
	<span id="asyncio-subprocess-protocols"></span><h3>Subprocess Protocols<a class="headerlink" href="#subprocess-protocols" title="Link to this heading">¶</a></h3>
	<p>Subprocess Protocol instances should be constructed by protocol
	factories passed to the <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.subprocess_exec" title="asyncio.loop.subprocess_exec"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.subprocess_exec()</span></code></a> and
	<a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.subprocess_shell" title="asyncio.loop.subprocess_shell"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.subprocess_shell()</span></code></a> methods.</p>
	<dl class="py method">
	<dt class="sig sig-object py" id="asyncio.SubprocessProtocol.pipe_data_received">
	<span class="sig-prename descclassname"><span class="pre">SubprocessProtocol.</span></span><span class="sig-name descname"><span class="pre">pipe_data_received</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">fd</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">data</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.SubprocessProtocol.pipe_data_received" title="Link to this definition">¶</a></dt>
	<dd><p>Called when the child process writes data into its stdout or stderr
	pipe.</p>
	<p><em>fd</em> is the integer file descriptor of the pipe.</p>
	<p><em>data</em> is a non-empty bytes object containing the received data.</p>
	</dd></dl>

	<dl class="py method">
	<dt class="sig sig-object py" id="asyncio.SubprocessProtocol.pipe_connection_lost">
	<span class="sig-prename descclassname"><span class="pre">SubprocessProtocol.</span></span><span class="sig-name descname"><span class="pre">pipe_connection_lost</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">fd</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">exc</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.SubprocessProtocol.pipe_connection_lost" title="Link to this definition">¶</a></dt>
	<dd><p>Called when one of the pipes communicating with the child process
	is closed.</p>
	<p><em>fd</em> is the integer file descriptor that was closed.</p>
	</dd></dl>

	<dl class="py method">
	<dt class="sig sig-object py" id="asyncio.SubprocessProtocol.process_exited">
	<span class="sig-prename descclassname"><span class="pre">SubprocessProtocol.</span></span><span class="sig-name descname"><span class="pre">process_exited</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#asyncio.SubprocessProtocol.process_exited" title="Link to this definition">¶</a></dt>
	<dd><p>Called when the child process has exited.</p>
	<p>It can be called before <a class="reference internal" href="#asyncio.SubprocessProtocol.pipe_data_received" title="asyncio.SubprocessProtocol.pipe_data_received"><code class="xref py py-meth docutils literal notranslate"><span class="pre">pipe_data_received()</span></code></a> and
	<a class="reference internal" href="#asyncio.SubprocessProtocol.pipe_connection_lost" title="asyncio.SubprocessProtocol.pipe_connection_lost"><code class="xref py py-meth docutils literal notranslate"><span class="pre">pipe_connection_lost()</span></code></a> methods.</p>
	</dd></dl>

	</section>
	</section>
	<section id="examples">
	<h2>Examples<a class="headerlink" href="#examples" title="Link to this heading">¶</a></h2>
	<section id="tcp-echo-server">
	<span id="asyncio-example-tcp-echo-server-protocol"></span><h3>TCP Echo Server<a class="headerlink" href="#tcp-echo-server" title="Link to this heading">¶</a></h3>
	<p>Create a TCP echo server using the <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.create_server" title="asyncio.loop.create_server"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.create_server()</span></code></a> method, send back
	received data, and close the connection:</p>
	<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span><span class="w"> </span><span class="nn">asyncio</span>


	<span class="k">class</span><span class="w"> </span><span class="nc">EchoServerProtocol</span><span class="p">(</span><span class="n">asyncio</span><span class="o">.</span><span class="n">Protocol</span><span class="p">):</span>
	<span class="k">def</span><span class="w"> </span><span class="nf">connection_made</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">transport</span><span class="p">):</span>
	<span class="n">peername</span> <span class="o">=</span> <span class="n">transport</span><span class="o">.</span><span class="n">get_extra_info</span><span class="p">(</span><span class="s1">'peername'</span><span class="p">)</span>
	<span class="nb">print</span><span class="p">(</span><span class="s1">'Connection from </span><span class="si">{}</span><span class="s1">'</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">peername</span><span class="p">))</span>
	<span class="bp">self</span><span class="o">.</span><span class="n">transport</span> <span class="o">=</span> <span class="n">transport</span>

	<span class="k">def</span><span class="w"> </span><span class="nf">data_received</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">data</span><span class="p">):</span>
	<span class="n">message</span> <span class="o">=</span> <span class="n">data</span><span class="o">.</span><span class="n">decode</span><span class="p">()</span>
	<span class="nb">print</span><span class="p">(</span><span class="s1">'Data received: </span><span class="si">{!r}</span><span class="s1">'</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">message</span><span class="p">))</span>

	<span class="nb">print</span><span class="p">(</span><span class="s1">'Send: </span><span class="si">{!r}</span><span class="s1">'</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">message</span><span class="p">))</span>
	<span class="bp">self</span><span class="o">.</span><span class="n">transport</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="n">data</span><span class="p">)</span>

	<span class="nb">print</span><span class="p">(</span><span class="s1">'Close the client socket'</span><span class="p">)</span>
	<span class="bp">self</span><span class="o">.</span><span class="n">transport</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>


	<span class="k">async</span> <span class="k">def</span><span class="w"> </span><span class="nf">main</span><span class="p">():</span>
	<span class="c1"># Get a reference to the event loop as we plan to use</span>
	<span class="c1"># low-level APIs.</span>
	<span class="n">loop</span> <span class="o">=</span> <span class="n">asyncio</span><span class="o">.</span><span class="n">get_running_loop</span><span class="p">()</span>

	<span class="n">server</span> <span class="o">=</span> <span class="k">await</span> <span class="n">loop</span><span class="o">.</span><span class="n">create_server</span><span class="p">(</span>
	<span class="n">EchoServerProtocol</span><span class="p">,</span>
	<span class="s1">'127.0.0.1'</span><span class="p">,</span> <span class="mi">8888</span><span class="p">)</span>

	<span class="k">async</span> <span class="k">with</span> <span class="n">server</span><span class="p">:</span>
	<span class="k">await</span> <span class="n">server</span><span class="o">.</span><span class="n">serve_forever</span><span class="p">()</span>


	<span class="n">asyncio</span><span class="o">.</span><span class="n">run</span><span class="p">(</span><span class="n">main</span><span class="p">())</span>
	</pre></div>
	</div>
	<div class="admonition seealso">
	<p class="admonition-title">See also</p>
	<p>The <a class="reference internal" href="asyncio-stream.html#asyncio-tcp-echo-server-streams"><span class="std std-ref">TCP echo server using streams</span></a>
	example uses the high-level <a class="reference internal" href="asyncio-stream.html#asyncio.start_server" title="asyncio.start_server"><code class="xref py py-func docutils literal notranslate"><span class="pre">asyncio.start_server()</span></code></a> function.</p>
	</div>
	</section>
	<section id="tcp-echo-client">
	<span id="asyncio-example-tcp-echo-client-protocol"></span><h3>TCP Echo Client<a class="headerlink" href="#tcp-echo-client" title="Link to this heading">¶</a></h3>
	<p>A TCP echo client using the <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.create_connection" title="asyncio.loop.create_connection"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.create_connection()</span></code></a> method, sends
	data, and waits until the connection is closed:</p>
	<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span><span class="w"> </span><span class="nn">asyncio</span>


	<span class="k">class</span><span class="w"> </span><span class="nc">EchoClientProtocol</span><span class="p">(</span><span class="n">asyncio</span><span class="o">.</span><span class="n">Protocol</span><span class="p">):</span>
	<span class="k">def</span><span class="w"> </span><span class="fm">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">message</span><span class="p">,</span> <span class="n">on_con_lost</span><span class="p">):</span>
	<span class="bp">self</span><span class="o">.</span><span class="n">message</span> <span class="o">=</span> <span class="n">message</span>
	<span class="bp">self</span><span class="o">.</span><span class="n">on_con_lost</span> <span class="o">=</span> <span class="n">on_con_lost</span>

	<span class="k">def</span><span class="w"> </span><span class="nf">connection_made</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">transport</span><span class="p">):</span>
	<span class="n">transport</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">message</span><span class="o">.</span><span class="n">encode</span><span class="p">())</span>
	<span class="nb">print</span><span class="p">(</span><span class="s1">'Data sent: </span><span class="si">{!r}</span><span class="s1">'</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">message</span><span class="p">))</span>

	<span class="k">def</span><span class="w"> </span><span class="nf">data_received</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">data</span><span class="p">):</span>
	<span class="nb">print</span><span class="p">(</span><span class="s1">'Data received: </span><span class="si">{!r}</span><span class="s1">'</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">data</span><span class="o">.</span><span class="n">decode</span><span class="p">()))</span>

	<span class="k">def</span><span class="w"> </span><span class="nf">connection_lost</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">exc</span><span class="p">):</span>
	<span class="nb">print</span><span class="p">(</span><span class="s1">'The server closed the connection'</span><span class="p">)</span>
	<span class="bp">self</span><span class="o">.</span><span class="n">on_con_lost</span><span class="o">.</span><span class="n">set_result</span><span class="p">(</span><span class="kc">True</span><span class="p">)</span>


	<span class="k">async</span> <span class="k">def</span><span class="w"> </span><span class="nf">main</span><span class="p">():</span>
	<span class="c1"># Get a reference to the event loop as we plan to use</span>
	<span class="c1"># low-level APIs.</span>
	<span class="n">loop</span> <span class="o">=</span> <span class="n">asyncio</span><span class="o">.</span><span class="n">get_running_loop</span><span class="p">()</span>

	<span class="n">on_con_lost</span> <span class="o">=</span> <span class="n">loop</span><span class="o">.</span><span class="n">create_future</span><span class="p">()</span>
	<span class="n">message</span> <span class="o">=</span> <span class="s1">'Hello World!'</span>

	<span class="n">transport</span><span class="p">,</span> <span class="n">protocol</span> <span class="o">=</span> <span class="k">await</span> <span class="n">loop</span><span class="o">.</span><span class="n">create_connection</span><span class="p">(</span>
	<span class="k">lambda</span><span class="p">:</span> <span class="n">EchoClientProtocol</span><span class="p">(</span><span class="n">message</span><span class="p">,</span> <span class="n">on_con_lost</span><span class="p">),</span>
	<span class="s1">'127.0.0.1'</span><span class="p">,</span> <span class="mi">8888</span><span class="p">)</span>

	<span class="c1"># Wait until the protocol signals that the connection</span>
	<span class="c1"># is lost and close the transport.</span>
	<span class="k">try</span><span class="p">:</span>
	<span class="k">await</span> <span class="n">on_con_lost</span>
	<span class="k">finally</span><span class="p">:</span>
	<span class="n">transport</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>


	<span class="n">asyncio</span><span class="o">.</span><span class="n">run</span><span class="p">(</span><span class="n">main</span><span class="p">())</span>
	</pre></div>
	</div>
	<div class="admonition seealso">
	<p class="admonition-title">See also</p>
	<p>The <a class="reference internal" href="asyncio-stream.html#asyncio-tcp-echo-client-streams"><span class="std std-ref">TCP echo client using streams</span></a>
	example uses the high-level <a class="reference internal" href="asyncio-stream.html#asyncio.open_connection" title="asyncio.open_connection"><code class="xref py py-func docutils literal notranslate"><span class="pre">asyncio.open_connection()</span></code></a> function.</p>
	</div>
	</section>
	<section id="udp-echo-server">
	<span id="asyncio-udp-echo-server-protocol"></span><h3>UDP Echo Server<a class="headerlink" href="#udp-echo-server" title="Link to this heading">¶</a></h3>
	<p>A UDP echo server, using the <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.create_datagram_endpoint" title="asyncio.loop.create_datagram_endpoint"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.create_datagram_endpoint()</span></code></a>
	method, sends back received data:</p>
	<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span><span class="w"> </span><span class="nn">asyncio</span>


	<span class="k">class</span><span class="w"> </span><span class="nc">EchoServerProtocol</span><span class="p">:</span>
	<span class="k">def</span><span class="w"> </span><span class="nf">connection_made</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">transport</span><span class="p">):</span>
	<span class="bp">self</span><span class="o">.</span><span class="n">transport</span> <span class="o">=</span> <span class="n">transport</span>

	<span class="k">def</span><span class="w"> </span><span class="nf">datagram_received</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">data</span><span class="p">,</span> <span class="n">addr</span><span class="p">):</span>
	<span class="n">message</span> <span class="o">=</span> <span class="n">data</span><span class="o">.</span><span class="n">decode</span><span class="p">()</span>
	<span class="nb">print</span><span class="p">(</span><span class="s1">'Received </span><span class="si">%r</span><span class="s1"> from </span><span class="si">%s</span><span class="s1">'</span> <span class="o">%</span> <span class="p">(</span><span class="n">message</span><span class="p">,</span> <span class="n">addr</span><span class="p">))</span>
	<span class="nb">print</span><span class="p">(</span><span class="s1">'Send </span><span class="si">%r</span><span class="s1"> to </span><span class="si">%s</span><span class="s1">'</span> <span class="o">%</span> <span class="p">(</span><span class="n">message</span><span class="p">,</span> <span class="n">addr</span><span class="p">))</span>
	<span class="bp">self</span><span class="o">.</span><span class="n">transport</span><span class="o">.</span><span class="n">sendto</span><span class="p">(</span><span class="n">data</span><span class="p">,</span> <span class="n">addr</span><span class="p">)</span>


	<span class="k">async</span> <span class="k">def</span><span class="w"> </span><span class="nf">main</span><span class="p">():</span>
	<span class="nb">print</span><span class="p">(</span><span class="s2">"Starting UDP server"</span><span class="p">)</span>

	<span class="c1"># Get a reference to the event loop as we plan to use</span>
	<span class="c1"># low-level APIs.</span>
	<span class="n">loop</span> <span class="o">=</span> <span class="n">asyncio</span><span class="o">.</span><span class="n">get_running_loop</span><span class="p">()</span>

	<span class="c1"># One protocol instance will be created to serve all</span>
	<span class="c1"># client requests.</span>
	<span class="n">transport</span><span class="p">,</span> <span class="n">protocol</span> <span class="o">=</span> <span class="k">await</span> <span class="n">loop</span><span class="o">.</span><span class="n">create_datagram_endpoint</span><span class="p">(</span>
	<span class="n">EchoServerProtocol</span><span class="p">,</span>
	<span class="n">local_addr</span><span class="o">=</span><span class="p">(</span><span class="s1">'127.0.0.1'</span><span class="p">,</span> <span class="mi">9999</span><span class="p">))</span>

	<span class="k">try</span><span class="p">:</span>
	<span class="k">await</span> <span class="n">asyncio</span><span class="o">.</span><span class="n">sleep</span><span class="p">(</span><span class="mi">3600</span><span class="p">)</span> <span class="c1"># Serve for 1 hour.</span>
	<span class="k">finally</span><span class="p">:</span>
	<span class="n">transport</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>


	<span class="n">asyncio</span><span class="o">.</span><span class="n">run</span><span class="p">(</span><span class="n">main</span><span class="p">())</span>
	</pre></div>
	</div>
	</section>
	<section id="udp-echo-client">
	<span id="asyncio-udp-echo-client-protocol"></span><h3>UDP Echo Client<a class="headerlink" href="#udp-echo-client" title="Link to this heading">¶</a></h3>
	<p>A UDP echo client, using the <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.create_datagram_endpoint" title="asyncio.loop.create_datagram_endpoint"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.create_datagram_endpoint()</span></code></a>
	method, sends data and closes the transport when it receives the answer:</p>
	<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span><span class="w"> </span><span class="nn">asyncio</span>


	<span class="k">class</span><span class="w"> </span><span class="nc">EchoClientProtocol</span><span class="p">:</span>
	<span class="k">def</span><span class="w"> </span><span class="fm">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">message</span><span class="p">,</span> <span class="n">on_con_lost</span><span class="p">):</span>
	<span class="bp">self</span><span class="o">.</span><span class="n">message</span> <span class="o">=</span> <span class="n">message</span>
	<span class="bp">self</span><span class="o">.</span><span class="n">on_con_lost</span> <span class="o">=</span> <span class="n">on_con_lost</span>
	<span class="bp">self</span><span class="o">.</span><span class="n">transport</span> <span class="o">=</span> <span class="kc">None</span>

	<span class="k">def</span><span class="w"> </span><span class="nf">connection_made</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">transport</span><span class="p">):</span>
	<span class="bp">self</span><span class="o">.</span><span class="n">transport</span> <span class="o">=</span> <span class="n">transport</span>
	<span class="nb">print</span><span class="p">(</span><span class="s1">'Send:'</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">message</span><span class="p">)</span>
	<span class="bp">self</span><span class="o">.</span><span class="n">transport</span><span class="o">.</span><span class="n">sendto</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">message</span><span class="o">.</span><span class="n">encode</span><span class="p">())</span>

	<span class="k">def</span><span class="w"> </span><span class="nf">datagram_received</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">data</span><span class="p">,</span> <span class="n">addr</span><span class="p">):</span>
	<span class="nb">print</span><span class="p">(</span><span class="s2">"Received:"</span><span class="p">,</span> <span class="n">data</span><span class="o">.</span><span class="n">decode</span><span class="p">())</span>

	<span class="nb">print</span><span class="p">(</span><span class="s2">"Close the socket"</span><span class="p">)</span>
	<span class="bp">self</span><span class="o">.</span><span class="n">transport</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>

	<span class="k">def</span><span class="w"> </span><span class="nf">error_received</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">exc</span><span class="p">):</span>
	<span class="nb">print</span><span class="p">(</span><span class="s1">'Error received:'</span><span class="p">,</span> <span class="n">exc</span><span class="p">)</span>

	<span class="k">def</span><span class="w"> </span><span class="nf">connection_lost</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">exc</span><span class="p">):</span>
	<span class="nb">print</span><span class="p">(</span><span class="s2">"Connection closed"</span><span class="p">)</span>
	<span class="bp">self</span><span class="o">.</span><span class="n">on_con_lost</span><span class="o">.</span><span class="n">set_result</span><span class="p">(</span><span class="kc">True</span><span class="p">)</span>


	<span class="k">async</span> <span class="k">def</span><span class="w"> </span><span class="nf">main</span><span class="p">():</span>
	<span class="c1"># Get a reference to the event loop as we plan to use</span>
	<span class="c1"># low-level APIs.</span>
	<span class="n">loop</span> <span class="o">=</span> <span class="n">asyncio</span><span class="o">.</span><span class="n">get_running_loop</span><span class="p">()</span>

	<span class="n">on_con_lost</span> <span class="o">=</span> <span class="n">loop</span><span class="o">.</span><span class="n">create_future</span><span class="p">()</span>
	<span class="n">message</span> <span class="o">=</span> <span class="s2">"Hello World!"</span>

	<span class="n">transport</span><span class="p">,</span> <span class="n">protocol</span> <span class="o">=</span> <span class="k">await</span> <span class="n">loop</span><span class="o">.</span><span class="n">create_datagram_endpoint</span><span class="p">(</span>
	<span class="k">lambda</span><span class="p">:</span> <span class="n">EchoClientProtocol</span><span class="p">(</span><span class="n">message</span><span class="p">,</span> <span class="n">on_con_lost</span><span class="p">),</span>
	<span class="n">remote_addr</span><span class="o">=</span><span class="p">(</span><span class="s1">'127.0.0.1'</span><span class="p">,</span> <span class="mi">9999</span><span class="p">))</span>

	<span class="k">try</span><span class="p">:</span>
	<span class="k">await</span> <span class="n">on_con_lost</span>
	<span class="k">finally</span><span class="p">:</span>
	<span class="n">transport</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>


	<span class="n">asyncio</span><span class="o">.</span><span class="n">run</span><span class="p">(</span><span class="n">main</span><span class="p">())</span>
	</pre></div>
	</div>
	</section>
	<section id="connecting-existing-sockets">
	<span id="asyncio-example-create-connection"></span><h3>Connecting Existing Sockets<a class="headerlink" href="#connecting-existing-sockets" title="Link to this heading">¶</a></h3>
	<p>Wait until a socket receives data using the
	<a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.create_connection" title="asyncio.loop.create_connection"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.create_connection()</span></code></a> method with a protocol:</p>
	<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span><span class="w"> </span><span class="nn">asyncio</span>
	<span class="kn">import</span><span class="w"> </span><span class="nn">socket</span>


	<span class="k">class</span><span class="w"> </span><span class="nc">MyProtocol</span><span class="p">(</span><span class="n">asyncio</span><span class="o">.</span><span class="n">Protocol</span><span class="p">):</span>

	<span class="k">def</span><span class="w"> </span><span class="fm">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">on_con_lost</span><span class="p">):</span>
	<span class="bp">self</span><span class="o">.</span><span class="n">transport</span> <span class="o">=</span> <span class="kc">None</span>
	<span class="bp">self</span><span class="o">.</span><span class="n">on_con_lost</span> <span class="o">=</span> <span class="n">on_con_lost</span>

	<span class="k">def</span><span class="w"> </span><span class="nf">connection_made</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">transport</span><span class="p">):</span>
	<span class="bp">self</span><span class="o">.</span><span class="n">transport</span> <span class="o">=</span> <span class="n">transport</span>

	<span class="k">def</span><span class="w"> </span><span class="nf">data_received</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">data</span><span class="p">):</span>
	<span class="nb">print</span><span class="p">(</span><span class="s2">"Received:"</span><span class="p">,</span> <span class="n">data</span><span class="o">.</span><span class="n">decode</span><span class="p">())</span>

	<span class="c1"># We are done: close the transport;</span>
	<span class="c1"># connection_lost() will be called automatically.</span>
	<span class="bp">self</span><span class="o">.</span><span class="n">transport</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>

	<span class="k">def</span><span class="w"> </span><span class="nf">connection_lost</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">exc</span><span class="p">):</span>
	<span class="c1"># The socket has been closed</span>
	<span class="bp">self</span><span class="o">.</span><span class="n">on_con_lost</span><span class="o">.</span><span class="n">set_result</span><span class="p">(</span><span class="kc">True</span><span class="p">)</span>


	<span class="k">async</span> <span class="k">def</span><span class="w"> </span><span class="nf">main</span><span class="p">():</span>
	<span class="c1"># Get a reference to the event loop as we plan to use</span>
	<span class="c1"># low-level APIs.</span>
	<span class="n">loop</span> <span class="o">=</span> <span class="n">asyncio</span><span class="o">.</span><span class="n">get_running_loop</span><span class="p">()</span>
	<span class="n">on_con_lost</span> <span class="o">=</span> <span class="n">loop</span><span class="o">.</span><span class="n">create_future</span><span class="p">()</span>

	<span class="c1"># Create a pair of connected sockets</span>
	<span class="n">rsock</span><span class="p">,</span> <span class="n">wsock</span> <span class="o">=</span> <span class="n">socket</span><span class="o">.</span><span class="n">socketpair</span><span class="p">()</span>

	<span class="c1"># Register the socket to wait for data.</span>
	<span class="n">transport</span><span class="p">,</span> <span class="n">protocol</span> <span class="o">=</span> <span class="k">await</span> <span class="n">loop</span><span class="o">.</span><span class="n">create_connection</span><span class="p">(</span>
	<span class="k">lambda</span><span class="p">:</span> <span class="n">MyProtocol</span><span class="p">(</span><span class="n">on_con_lost</span><span class="p">),</span> <span class="n">sock</span><span class="o">=</span><span class="n">rsock</span><span class="p">)</span>

	<span class="c1"># Simulate the reception of data from the network.</span>
	<span class="n">loop</span><span class="o">.</span><span class="n">call_soon</span><span class="p">(</span><span class="n">wsock</span><span class="o">.</span><span class="n">send</span><span class="p">,</span> <span class="s1">'abc'</span><span class="o">.</span><span class="n">encode</span><span class="p">())</span>

	<span class="k">try</span><span class="p">:</span>
	<span class="k">await</span> <span class="n">protocol</span><span class="o">.</span><span class="n">on_con_lost</span>
	<span class="k">finally</span><span class="p">:</span>
	<span class="n">transport</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>
	<span class="n">wsock</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>

	<span class="n">asyncio</span><span class="o">.</span><span class="n">run</span><span class="p">(</span><span class="n">main</span><span class="p">())</span>
	</pre></div>
	</div>
	<div class="admonition seealso">
	<p class="admonition-title">See also</p>
	<p>The <a class="reference internal" href="asyncio-eventloop.html#asyncio-example-watch-fd"><span class="std std-ref">watch a file descriptor for read events</span></a> example uses the low-level
	<a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.add_reader" title="asyncio.loop.add_reader"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.add_reader()</span></code></a> method to register an FD.</p>
	<p>The <a class="reference internal" href="asyncio-stream.html#asyncio-example-create-connection-streams"><span class="std std-ref">register an open socket to wait for data using streams</span></a> example uses high-level streams
	created by the <a class="reference internal" href="asyncio-stream.html#asyncio.open_connection" title="asyncio.open_connection"><code class="xref py py-func docutils literal notranslate"><span class="pre">open_connection()</span></code></a> function in a coroutine.</p>
	</div>
	</section>
	<section id="loop-subprocess-exec-and-subprocessprotocol">
	<span id="asyncio-example-subprocess-proto"></span><h3>loop.subprocess_exec() and SubprocessProtocol<a class="headerlink" href="#loop-subprocess-exec-and-subprocessprotocol" title="Link to this heading">¶</a></h3>
	<p>An example of a subprocess protocol used to get the output of a
	subprocess and to wait for the subprocess exit.</p>
	<p>The subprocess is created by the <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.subprocess_exec" title="asyncio.loop.subprocess_exec"><code class="xref py py-meth docutils literal notranslate"><span class="pre">loop.subprocess_exec()</span></code></a> method:</p>
	<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span><span class="w"> </span><span class="nn">asyncio</span>
	<span class="kn">import</span><span class="w"> </span><span class="nn">sys</span>

	<span class="k">class</span><span class="w"> </span><span class="nc">DateProtocol</span><span class="p">(</span><span class="n">asyncio</span><span class="o">.</span><span class="n">SubprocessProtocol</span><span class="p">):</span>
	<span class="k">def</span><span class="w"> </span><span class="fm">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">exit_future</span><span class="p">):</span>
	<span class="bp">self</span><span class="o">.</span><span class="n">exit_future</span> <span class="o">=</span> <span class="n">exit_future</span>
	<span class="bp">self</span><span class="o">.</span><span class="n">output</span> <span class="o">=</span> <span class="nb">bytearray</span><span class="p">()</span>
	<span class="bp">self</span><span class="o">.</span><span class="n">pipe_closed</span> <span class="o">=</span> <span class="kc">False</span>
	<span class="bp">self</span><span class="o">.</span><span class="n">exited</span> <span class="o">=</span> <span class="kc">False</span>

	<span class="k">def</span><span class="w"> </span><span class="nf">pipe_connection_lost</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">fd</span><span class="p">,</span> <span class="n">exc</span><span class="p">):</span>
	<span class="bp">self</span><span class="o">.</span><span class="n">pipe_closed</span> <span class="o">=</span> <span class="kc">True</span>
	<span class="bp">self</span><span class="o">.</span><span class="n">check_for_exit</span><span class="p">()</span>

	<span class="k">def</span><span class="w"> </span><span class="nf">pipe_data_received</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">fd</span><span class="p">,</span> <span class="n">data</span><span class="p">):</span>
	<span class="bp">self</span><span class="o">.</span><span class="n">output</span><span class="o">.</span><span class="n">extend</span><span class="p">(</span><span class="n">data</span><span class="p">)</span>

	<span class="k">def</span><span class="w"> </span><span class="nf">process_exited</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
	<span class="bp">self</span><span class="o">.</span><span class="n">exited</span> <span class="o">=</span> <span class="kc">True</span>
	<span class="c1"># process_exited() method can be called before</span>
	<span class="c1"># pipe_connection_lost() method: wait until both methods are</span>
	<span class="c1"># called.</span>
	<span class="bp">self</span><span class="o">.</span><span class="n">check_for_exit</span><span class="p">()</span>

	<span class="k">def</span><span class="w"> </span><span class="nf">check_for_exit</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
	<span class="k">if</span> <span class="bp">self</span><span class="o">.</span><span class="n">pipe_closed</span> <span class="ow">and</span> <span class="bp">self</span><span class="o">.</span><span class="n">exited</span><span class="p">:</span>
	<span class="bp">self</span><span class="o">.</span><span class="n">exit_future</span><span class="o">.</span><span class="n">set_result</span><span class="p">(</span><span class="kc">True</span><span class="p">)</span>

	<span class="k">async</span> <span class="k">def</span><span class="w"> </span><span class="nf">get_date</span><span class="p">():</span>
	<span class="c1"># Get a reference to the event loop as we plan to use</span>
	<span class="c1"># low-level APIs.</span>
	<span class="n">loop</span> <span class="o">=</span> <span class="n">asyncio</span><span class="o">.</span><span class="n">get_running_loop</span><span class="p">()</span>

	<span class="n">code</span> <span class="o">=</span> <span class="s1">'import datetime; print(datetime.datetime.now())'</span>
	<span class="n">exit_future</span> <span class="o">=</span> <span class="n">asyncio</span><span class="o">.</span><span class="n">Future</span><span class="p">(</span><span class="n">loop</span><span class="o">=</span><span class="n">loop</span><span class="p">)</span>

	<span class="c1"># Create the subprocess controlled by DateProtocol;</span>
	<span class="c1"># redirect the standard output into a pipe.</span>
	<span class="n">transport</span><span class="p">,</span> <span class="n">protocol</span> <span class="o">=</span> <span class="k">await</span> <span class="n">loop</span><span class="o">.</span><span class="n">subprocess_exec</span><span class="p">(</span>
	<span class="k">lambda</span><span class="p">:</span> <span class="n">DateProtocol</span><span class="p">(</span><span class="n">exit_future</span><span class="p">),</span>
	<span class="n">sys</span><span class="o">.</span><span class="n">executable</span><span class="p">,</span> <span class="s1">'-c'</span><span class="p">,</span> <span class="n">code</span><span class="p">,</span>
	<span class="n">stdin</span><span class="o">=</span><span class="kc">None</span><span class="p">,</span> <span class="n">stderr</span><span class="o">=</span><span class="kc">None</span><span class="p">)</span>

	<span class="c1"># Wait for the subprocess exit using the process_exited()</span>
	<span class="c1"># method of the protocol.</span>
	<span class="k">await</span> <span class="n">exit_future</span>

	<span class="c1"># Close the stdout pipe.</span>
	<span class="n">transport</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>

	<span class="c1"># Read the output which was collected by the</span>
	<span class="c1"># pipe_data_received() method of the protocol.</span>
	<span class="n">data</span> <span class="o">=</span> <span class="nb">bytes</span><span class="p">(</span><span class="n">protocol</span><span class="o">.</span><span class="n">output</span><span class="p">)</span>
	<span class="k">return</span> <span class="n">data</span><span class="o">.</span><span class="n">decode</span><span class="p">(</span><span class="s1">'ascii'</span><span class="p">)</span><span class="o">.</span><span class="n">rstrip</span><span class="p">()</span>

	<span class="n">date</span> <span class="o">=</span> <span class="n">asyncio</span><span class="o">.</span><span class="n">run</span><span class="p">(</span><span class="n">get_date</span><span class="p">())</span>
	<span class="nb">print</span><span class="p">(</span><span class="sa">f</span><span class="s2">"Current date: </span><span class="si">{</span><span class="n">date</span><span class="si">}</span><span class="s2">"</span><span class="p">)</span>
	</pre></div>
	</div>
	<p>See also the <a class="reference internal" href="asyncio-subprocess.html#asyncio-example-create-subprocess-exec"><span class="std std-ref">same example</span></a>
	written using high-level APIs.</p>
	</section>
	</section>
	</section>


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	</div>
	</div>
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	<div>
	<h3><a href="../contents.html">Table of Contents</a></h3>
	<ul>
	<li><a class="reference internal" href="#">Transports and Protocols</a><ul>
	<li><a class="reference internal" href="#transports">Transports</a><ul>
	<li><a class="reference internal" href="#transports-hierarchy">Transports Hierarchy</a></li>
	<li><a class="reference internal" href="#base-transport">Base Transport</a></li>
	<li><a class="reference internal" href="#read-only-transports">Read-only Transports</a></li>
	<li><a class="reference internal" href="#write-only-transports">Write-only Transports</a></li>
	<li><a class="reference internal" href="#datagram-transports">Datagram Transports</a></li>
	<li><a class="reference internal" href="#subprocess-transports">Subprocess Transports</a></li>
	</ul>
	</li>
	<li><a class="reference internal" href="#protocols">Protocols</a><ul>
	<li><a class="reference internal" href="#base-protocols">Base Protocols</a></li>
	<li><a class="reference internal" href="#base-protocol">Base Protocol</a></li>
	<li><a class="reference internal" href="#streaming-protocols">Streaming Protocols</a></li>
	<li><a class="reference internal" href="#buffered-streaming-protocols">Buffered Streaming Protocols</a></li>
	<li><a class="reference internal" href="#datagram-protocols">Datagram Protocols</a></li>
	<li><a class="reference internal" href="#subprocess-protocols">Subprocess Protocols</a></li>
	</ul>
	</li>
	<li><a class="reference internal" href="#examples">Examples</a><ul>
	<li><a class="reference internal" href="#tcp-echo-server">TCP Echo Server</a></li>
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