Erlang_WebSocket_Server

Erlang_WebSocket_Server is a server-side implementation for the WebSocket Protocol written in Erlang. This library conforms to WebSocket draft-76.The library provides efficient ways of developoing systems which use WebSocket. Handshake process mainly uses the code written by davebryson and ENDOH Takanao.

davebryson:https://github.com/davebryson/erlang_websocket ENDOH Takano:https://github.com/MiCHiLU/erlang_websocket

Process Design Pattern

This library has the following process design pattern.

see FIGURE

Each socket sender and reciever are connected to a corresponding WebSocket client. A socket receiver receives WebSocket frames or error message and pass them to the receiver process. The receiver decode passed frames. The handler handles unframed data and errors. The sender frames handled data and sends them to the specific socket sender or broadcast to all except for the socket sender connected to source client. The sender can also send data to all socket senders. All you have to write is what the handler does.

Simple Echo Server

-module(echo_handler).
-compile(export_all).
-import(websocket_server, [unicast/2]).
go() ->
   websocket_server:start("localhost", 9000, ?MODULE, default_echo_handler, []).
default_echo_handler() ->
  receive
    {message, Data, ConnectionID} -> 
      unicast(Data, ConnectionID),
      default_echo_handler();
    _Any -> default_echo_handler()
  end.

General Server

-module(general_handler).
-import(websocket_server, [unicast/2, broadcast/2, sendall/1]).
-compile(export_all).

go() ->
   websocket_server:start("localhost", 9000, ?MODULE, general_handler, []).
general_handler() ->
  receive
    {open, SocketSenderPid} ->
	%%do something when a connection opend.
    {message, Data, SocketSenderPid} -> 
	%%do something when the handler received data.
    {closed, SocketSenderPid} ->
	%%do something when a connection closed.
    {error, PosixReason, SocketSenderPid}
	%%do something when the handler received an error.
  end.

Demonstration

A demonstration of a WebSocket server which uses this library. http://etsukata.com/erl/cvws.html

Requirements

Erlang R14B or greater.

Getting Started

Server side: git clone git://github.com/Etsukata/erlang_websocket_server.git cd erlang_websocket_server/src/ make erl -s websocket_server start Client side: open Chrome browser javascript console var ws = new WebSocket("ws://localhost:9000"); ws.onmessage = function(m) { console.log(m) }; ws.send("hello");