npm package: @mcesystems/zeromq
Description: Next-generation ZeroMQ bindings for Node.js
Author: Rolf Timmermans
Latest version: 6.0.0-beta.6

# ZeroMQ.js Next Generation

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## ⚠️ Version 6.0.0 (in beta) features a brand new API that solves many fundamental issues and is recommended for new projects. For the current stable version see the [5.x branch](https://github.com/zeromq/zeromq.js/tree/5.x) ⚠️

[ØMQ](http://zeromq.org) bindings for Node.js. The goals of this library are:
* Semantically similar to the [native](https://github.com/zeromq/libzmq) ØMQ library, while sticking to JavaScript idioms.
* Use modern JavaScript and Node.js features such as `async`/`await` and async iterators.
* High performance.
* Fully usable with TypeScript (3.6+).

The API reference [can be found here](http://zeromq.github.io/zeromq.js/globals.html).


# Table of contents

* [Installation](#installation)
   * [Prebuilt binaries](#prebuilt-binaries)
   * [Building from source](#building-from-source)
* [Examples](#examples)
   * [Push/Pull](#pushpull)
   * [Pub/Sub](#pubsub)
   * [Compatibility layer for version 4/5](#compatibility-layer-for-version-45)
* [Contribution](#contribution)
* [History](#history)


# Installation

Install ZeroMQ.js with prebuilt binaries:

```sh
npm install zeromq@6.0.0-beta.5
```

Requirements for prebuilt binaries:

* Node.js 10.2+ or Electron 3+ (requires a [N-API](https://nodejs.org/api/n-api.html) version 3+)


## Prebuilt binaries

The following platforms have a **prebuilt binary** available:

* Linux on x86-64/armv7/armv8 with libstdc++.so.6.0.21+ (glibc++ 3.4.21+), for example:
  * Debian 9+ (Stretch or later)
  * Ubuntu 16.04+ (Xenial or later)
  * CentOS 8+
* Linux on x86-64 with musl, for example:
  * Alpine 3.3+
* MacOS 10.9+ on x86-64
* Windows on x86/x86-64

If a prebuilt binary is not available for your platform, installing will attempt to start a build from source.

## Building from source

If a prebuilt binary is unavailable or if you want to pass certain options during build, you can build this package from source.

Make sure you have the following installed before attempting to build from source:

* Node.js 10+ or Electron 3+
* A working C++17 compiler toolchain with make
* Python 2.7 (or Python 3 with Node 12.13+)
* CMake 2.8+
* curl

To install from source

```sh
npm install zeromq@6.0.0-beta.5 --build-from-source
```

If you want to link against a shared ZeroMQ library, you can build skip downloading libzmq and link with the installed library instead as follows:

```sh
npm install zeromq@6.0.0-beta.5 --zmq-shared
```

If you wish to use any DRAFT sockets then it is also necessary to compile the library from source:

```sh
npm install zeromq@6.0.0-beta.5 --zmq-draft
```

# Examples

**Note:** The examples assume the reader is familiar with ZeroMQ. If you are new to ZeroMQ, please start with the [ZeroMQ documentation](https://zeromq.org/get-started/).

More examples can be found in the [examples directory](examples).

## Push/Pull

This example demonstrates how a producer pushes information onto a
socket and how a worker pulls information from the socket.

### producer.js

```js
const zmq = require("zeromq")

async function run() {
  const sock = new zmq.Push

  await sock.bind("tcp://127.0.0.1:3000")
  console.log("Producer bound to port 3000")

  while (true) {
    await sock.send("some work")
    await new Promise(resolve => setTimeout(resolve, 500))
  }
}

run()
```

### worker.js

```js
const zmq = require("zeromq")

async function run() {
  const sock = new zmq.Pull

  sock.connect("tcp://127.0.0.1:3000")
  console.log("Worker connected to port 3000")

  for await (const [msg] of sock) {
    console.log("work: %s", msg.toString())
  }
}

run()
```


## Pub/Sub

This example demonstrates using `zeromq` in a classic Pub/Sub,
Publisher/Subscriber, application.

### publisher.js

```js
const zmq = require("zeromq")

async function run() {
  const sock = new zmq.Publisher

  await sock.bind("tcp://127.0.0.1:3000")
  console.log("Publisher bound to port 3000")

  while (true) {
    console.log("sending a multipart message envelope")
    await sock.send(["kitty cats", "meow!"])
    await new Promise(resolve => setTimeout(resolve, 500))
  }
}

run()
```

### subscriber.js

```js
const zmq = require("zeromq")

async function run() {
  const sock = new zmq.Subscriber

  sock.connect("tcp://127.0.0.1:3000")
  sock.subscribe("kitty cats")
  console.log("Subscriber connected to port 3000")

  for await (const [topic, msg] of sock) {
    console.log("received a message related to:", topic, "containing message:", msg)
  }
}

run()
```


## Compatibility layer for version 4/5

The next generation version of the library features a compatibility layer for ZeroMQ.js versions 4 and 5. This is recommended for users upgrading from previous versions.

Example:

```js
const zmq = require("zeromq/v5-compat")

const pub = zmq.socket("pub")
const sub = zmq.socket("sub")

pub.bind("tcp://*:3456", err => {
  if (err) throw err

  sub.connect("tcp://127.0.0.1:3456")

  pub.send("message")

  sub.on("message", msg => {
    // Handle received message...
  })
})
```


# Contribution


## Dependencies

In order to develop and test the library, you'll need the tools required to build from source ([see above](#building-from-source)).

Additionally, having clang-format is strongly recommended.


## Defining new options

Socket and context options can be set at runtime, even if they are not implemented by this library. By design, this requires no recompilation if the built version of ZeroMQ has support for them. This allows library users to test and use options that have been introduced in recent versions of ZeroMQ without having to modify this library. Of course we'd love to include support for new options in an idiomatic way.

Options can be set as follows:

```js
const {Dealer} = require("zeromq")

/* This defines an accessor named 'sendHighWaterMark', which corresponds to
   the constant ZMQ_SNDHWM, which is defined as '23' in zmq.h. The option takes
   integers. The accessor name has been converted to idiomatic JavaScript.
   Of course, this particular option already exists in this library. */
class MyDealer extends Dealer {
  get sendHighWaterMark(): number {
    return this.getInt32Option(23)
  }

  set sendHighWaterMark(value: number) {
    this.setInt32Option(23, value)
  }
}

const sock = new MyDealer({sendHighWaterMark: 456})
```

When submitting pull requests for new socket/context options, please consider the following:

* The option is documented in the TypeScript interface.
* The option is only added to relevant socket types, and if the ZMQ_ constant has a prefix indicating which type it applies to, it is stripped from the name as it is exposed in JavaScript.
* The name as exposed in this library is idiomatic for JavaScript, spelling out any abbreviations and using proper `camelCase` naming conventions.
* The option is a value that can be set on a socket, and you don't think it should actually be a method.


## Testing

The test suite can be run with:

```sh
npm install
npm run dev:build
npm run dev:test
```

Or, if you prefer:

```sh
yarn
yarn run dev:build
yarn run dev:test
```

The test suite will validate and fix the coding style, run all unit tests and verify the validity of the included TypeScript type definitions.

Some tests are not enabled by default:

* API Compatibility tests from ZeroMQ 5.x have been disabled by default. You can include the tests with `INCLUDE_COMPAT_TESTS=1 npm run dev:test`
* Some transports are not reliable on some older versions of ZeroMQ, the relevant tests will be skipped for those versions automatically.


## Publishing

To publish a new version, run:

```sh
npm version <new version>
git push && git push --tags
```

Wait for continuous integration to finish. Prebuilds will be generated for all supported platforms and attached to a Github release. Documentation is automatically generated and committed to `gh-pages`. Finally, a new NPM package version will be automatically released.


# History

Version 6+ is a complete rewrite of previous versions of ZeroMQ.js in order to be more reliable, correct, and usable in modern JavaScript & TypeScript code as first outlined in [this issue](https://github.com/zeromq/zeromq.js/issues/189). Previous versions of ZeroMQ.js were based on `zmq` and a fork that included prebuilt binaries.

See detailed changes in the [CHANGELOG](CHANGELOG.md).