# send

## PROLOG



           This manual page is part of the POSIX Programmer's Manual.  The
           Linux implementation of this interface may differ (consult the
           corresponding Linux manual page for details of Linux behavior), or
           the interface may not be implemented on Linux.
    


## NAME



           send — send a message on a socket
    


## SYNOPSIS



           #include <sys/socket.h>
    
           ssize_t send(int _socket_ , const void *_buffer_ , size_t _length_ , int _flags_);
    


## DESCRIPTION



           The _send_() function shall initiate transmission of a message from
           the specified socket to its peer. The _send_() function shall send a
           message only when the socket is connected. If the socket is a
           connectionless-mode socket, the message shall be sent to the pre-
           specified peer address.
    
           The _send_() function takes the following arguments:
    
           _socket_      Specifies the socket file descriptor.
    
           _buffer_      Points to the buffer containing the message to send.
    
           _length_      Specifies the length of the message in bytes.
    
           _flags_       Specifies the type of message transmission. Values of
                       this argument are formed by logically OR'ing zero or
                       more of the following flags:
    
                       MSG_EOR       Terminates a record (if supported by the
                                     protocol).
    
                       MSG_OOB       Sends out-of-band data on sockets that
                                     support out-of-band communications. The
                                     significance and semantics of out-of-
                                     band data are protocol-specific.
    
                       MSG_NOSIGNAL  Requests not to send the SIGPIPE signal
                                     if an attempt to send is made on a
                                     stream-oriented socket that is no longer
                                     connected. The **[EPIPE]** error shall still
                                     be returned.
    
           The length of the message to be sent is specified by the _length_
           argument. If the message is too long to pass through the
           underlying protocol, _send_() shall fail and no data shall be
           transmitted.
    
           Successful completion of a call to _send_() does not guarantee
           delivery of the message. A return value of -1 indicates only
           locally-detected errors.
    
           If space is not available at the sending socket to hold the
           message to be transmitted, and the socket file descriptor does not
           have O_NONBLOCK set, _send_() shall block until space is available.
           If space is not available at the sending socket to hold the
           message to be transmitted, and the socket file descriptor does
           have O_NONBLOCK set, _send_() shall fail. The _select_() and _poll_()
           functions can be used to determine when it is possible to send
           more data.
    
           The socket in use may require the process to have appropriate
           privileges to use the _send_() function.
    


## RETURN VALUE



           Upon successful completion, _send_() shall return the number of
           bytes sent. Otherwise, -1 shall be returned and _errno_ set to
           indicate the error.
    


## ERRORS



           The _send_() function shall fail if:
    
           **EAGAIN** or **EWOULDBLOCK**
                  The socket's file descriptor is marked O_NONBLOCK and the
                  requested operation would block.
    
           **EBADF** The _socket_ argument is not a valid file descriptor.
    
           **ECONNRESET**
                  A connection was forcibly closed by a peer.
    
           **EDESTADDRREQ**
                  The socket is not connection-mode and no peer address is
                  set.
    
           **EINTR** A signal interrupted _send_() before any data was
                  transmitted.
    
           **EMSGSIZE**
                  The message is too large to be sent all at once, as the
                  socket requires.
    
           **ENOTCONN**
                  The socket is not connected.
    
           **ENOTSOCK**
                  The _socket_ argument does not refer to a socket.
    
           **EOPNOTSUPP**
                  The _socket_ argument is associated with a socket that does
                  not support one or more of the values set in _flags_.
    
           **EPIPE** The socket is shut down for writing, or the socket is
                  connection-mode and is no longer connected. In the latter
                  case, and if the socket is of type SOCK_STREAM or
                  SOCK_SEQPACKET and the MSG_NOSIGNAL flag is not set, the
                  SIGPIPE signal is generated to the calling thread.
    
           The _send_() function may fail if:
    
           **EACCES** The calling process does not have appropriate privileges.
    
           **EIO** An I/O error occurred while reading from or writing to the
                  file system.
    
           **ENETDOWN**
                  The local network interface used to reach the destination
                  is down.
    
           **ENETUNREACH**
                  No route to the network is present.
    
           **ENOBUFS**
                  Insufficient resources were available in the system to
                  perform the operation.
    
           _The following sections are informative._
    


## EXAMPLES



           None.
    


## APPLICATION USAGE



           If the _socket_ argument refers to a connection-mode socket, the
           _send_() function is equivalent to _sendto_() (with any value for the
           _dest_addr_ and _dest_len_ arguments, as they are ignored in this
           case). If the _socket_ argument refers to a socket and the _flags_
           argument is 0, the _send_() function is equivalent to _write_().
    


## RATIONALE



           None.
    


## FUTURE DIRECTIONS



           None.
    


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