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gwsocket gwsocket

What is it?

gwsocket is a simple, standalone, language-agnostic, RFC6455 compliant WebSocket Server, written in C. It sits between your application and the client's browser, giving fast bidirectional communication between these two with ease and flexibility. More info at:

gwsocket terminal

How it Works?

Very simple, just redirect the output from your application (stdout) to stdin or to file (named pipe) and let gwsocket transfer the data to the browser — That's it.

For example, tailing your server's logs into the browser couldn't be easier

# tail -f /var/log/nginx/access.log > /tmp/wspipein.fifo


# tail -f /var/log/nginx/access.log | gwsocket

You can also get the client's data into (stdin) your application. In fact, you can even send your favorite ncurses program's output to the browser. See screencast above.


  • Message Fragmentation per section 5.4
  • UTF-8 Handling
  • Framing (Text & Binary messages)
  • Multiplexed non-blocking network I/O
  • Ability to pipe data in/out in two different modes (stdin/stdout & strict mode)
  • Origin-based restriction
  • It passes the Autobahn Testsuite :)
  • and of course, Valgrind tested
  • missing something?, please feel free to post it on Github.

Why gwsocket?

I needed a fast, simple, no-dependencies, no libraries, RFC6455 compliant WebSocket Server written in C that I could use for version 1.0 of GoAccess by simply piping data in and out — WebSockets made easy!

More Examples?

gwsocket is language agnostic, look at the Man Page for more details and examples on how to receive data from the browser and how to send it to the browser.


Installing gwsocket is pretty easy. Just download, extract and compile it with:

$ wget
$ tar -xzvf gwsocket-0.4.tar.gz
$ cd gwsocket-0.4/
$ ./configure
$ make
# make install

No dependencies needed. How nice isn't it :), well almost, you need gcc, make, etc.

Build from GitHub

$ git clone
$ cd gwsocket
$ autoreconf -fiv
$ ./configure
$ make
# make install

Data Modes

In order to establish a channel between your application and the client's browser, gwsocket provides two methods that allow the user to send data in and out. The first one is through the use of the standard input (stdin), and the standard output (stdout). The second method is through a fixed-size header followed by the payload. See options below for more details.


The standard input/output is the simplest way of sending/receiving data to/from a client. However, it's limited to broadcasting messages to all clients. To send messages to or receive from a specific client, use the strict mode in the next section. See language specific examples here.

Strict Mode

gwsocket implements its own tiny protocol for sending/receiving data. In contrast to the stdin/stdout mode, the strict mode allows you to send/receive data to/from specific connected clients as well as to keep track of who opened/closed a WebSocket connection. It also gives you the ability to pack and send as much data as you would like on a single message. See language specific examples here.

Command Line / Config Options

The following options can be supplied to the command line.

Command Line Option Description
-p --port Specifies the port to bind.
-h --help Command line help.
-V --version Display version information and exit.
--access-log=<path/file> Specifies the path/file for the access log.
--addr=<addr> Specifies the address to bind.
--echo-mode Set the server to echo all received messages.
--max-frame-size=<bytes> Maximum size of a websocket frame.
--origin=<origin> Ensure clients send the specified origin header upon handshake.
--pipein=<path/file> Creates a named pipe (FIFO) that reads from on the given path/file.
--pipeout=<path/file> Creates a named pipe (FIFO) that writes to the given path/file.
--std Enable --stdin and --stdout.
--stdin Send stdin to the websocket.
--stdout Send received websocket data to stdout.
--strict Parse messages using strict mode. See man page for more details.
--ssl-cert=<cert.crt> Path to SSL certificate.
--ssl-key=<priv.key> Path to SSL private key.
--unix-socket=<addr> Specify UNIX-domain socket address to bind server to.


  • Support for epoll and kqueue
  • Add more command line options
  • Add configuration file
  • Please feel free to open an issue to discuss a new feature.


MIT Licensed


Any help on gwsocket is welcome. The most helpful way is to try it out and give feedback. Feel free to use the Github issue tracker and pull requests to discuss and submit code changes.