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websocketd

by joewalnes

joewalnes /websocketd

Turn any program that uses STDIN/STDOUT into a WebSocket server. Like inetd, but for WebSockets.

14.8K Stars 853 Forks Last release: over 2 years ago (v0.3.0) BSD 2-Clause "Simplified" License 309 Commits 25 Releases

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websocketd

websocketd

is a small command-line tool that will wrap an existing command-line interface program, and allow it to be accessed via a WebSocket.

WebSocket-capable applications can now be built very easily. As long as you can write an executable program that reads

STDIN

and writes to

STDOUT

, you can build a WebSocket server. Do it in Python, Ruby, Perl, Bash, .NET, C, Go, PHP, Java, Clojure, Scala, Groovy, Expect, Awk, VBScript, Haskell, Lua, R, whatever! No networking libraries necessary.

-@joewalnes

Details

Upon startup,

websocketd

will start a WebSocket server on a specified port, and listen for connections.

Upon a connection, it will fork the appropriate process, and disconnect the process when the WebSocket connection closes (and vice-versa).

Any message sent from the WebSocket client will be piped to the process's

STDIN

stream, followed by a

\n

newline.

Any text printed by the process to

STDOUT

shall be sent as a WebSocket message whenever a

\n

newline is encountered.

Download

If you're on a Mac, you can install

websocketd

using Homebrew. Just run

brew install websocketd

. For other operating systems, or if you don't want to use Homebrew, check out the link below.

Download for Linux, OS X and Windows

Quickstart

To get started, we'll create a WebSocket endpoint that will accept connections, then send back messages, counting to 10 with 1 second pause between each one, before disconnecting.

To show how simple it is, let's do it in Bash!

count.sh:

#!/bin/bash for ((COUNT = 1; COUNT \<= 10; COUNT++)); do echo $COUNT sleep 1 done

Before turning it into a WebSocket server, let's test it from the command line. The beauty of

websocketd

is that servers work equally well in the command line, or in shell scripts, as they do in the server - with no modifications required.

$ chmod +x count.sh $ ./count.sh 1 2 3 4 5 6 7 8 9 10

Now let's turn it into a WebSocket server:

$ websocketd --port=8080 ./count.sh

Finally, let's create a web-page to test it.

count.html:

<script>
  // helper function: log message to screen
  function log(msg) {
    document.getElementById('log').textContent += msg + '\n';
  }

  // setup websocket with callbacks
  var ws = new WebSocket('ws://localhost:8080/');
  ws.onopen = function() {
    log('CONNECT');
  };
  ws.onclose = function() {
    log('DISCONNECT');
  };
  ws.onmessage = function(event) {
    log('MESSAGE: ' + event.data);
  };
</script>

Open this page in your web-browser. It will even work if you open it directly from disk using a

file://

URL.

More Features

  • Very simple install. Just download the single executable for Linux, Mac or Windows and run it. Minimal dependencies, no installers, no package managers, no external libraries. Suitable for development and production servers.
  • Server side scripts can access details about the WebSocket HTTP request (e.g. remote host, query parameters, cookies, path, etc) via standard CGI environment variables.
  • As well as serving websocket daemons it also includes a static file server and classic CGI server for convenience.
  • Command line help available via
    websocketd --help
    .
  • Includes WebSocket developer console to make it easy to test your scripts before you've built a JavaScript frontend.
  • Examples in many programming languages are available to help you getting started.

User Manual

More documentation in the user manual

Example Projects

Got more examples? Open a pull request.

My Other Projects

And follow @joewalnes!

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