nssocket

An elegant way to define lightweight protocols on-top of TCP/TLS sockets in node.js

Motivation

Working within node.js it is very easy to write lightweight network protocols that communicate over TCP or TLS. The definition of such protocols often requires repeated (and tedious) parsing of individual TCP/TLS packets into a message header and some JSON body.

Installation

  [sudo] npm install nssocket

How it works

With nssocket this tedious bookkeeping work is done automatically for you in two ways:

1. Leverages wildcard and namespaced events from EventEmitter2
2. Automatically serializes messages passed to .send() and deserializes messages from data events.
3. Implements default reconnect logic for potentially faulty connections.
4. Automatically wraps TCP connections with TLS using a known workaround

Messages

Messages in nssocket are serialized JSON arrays of the following form:

  ["namespace", "to", "event", { "this": "is", "the": "payload" }]

Although this is not as optimal as other message formats (pure binary, msgpack) most of your applications are probably IO-bound, and not by the computation time needed for serialization / deserialization. When working with NsSocket instances, all events are namespaced under data to avoid collision with other events.

Simple Example

  var nssocket = require('nssocket');

  //
  // Create an `nssocket` TCP server
  //
  var server = nssocket.createServer(function (socket) {
    //
    // Here `socket` will be an instance of `nssocket.NsSocket`.
    //
    socket.send(['you', 'there']);
    socket.data(['iam', 'here'], function (data) {
      //
      // Good! The socket speaks our language 
      // (i.e. simple 'you::there', 'iam::here' protocol)
      //
      // { iam: true, indeedHere: true }
      //
      console.dir(data);
    })
  });
  
  //
  // Tell the server to listen on port `6785` and then connect to it
  // using another NsSocket instance.
  //
  server.listen(6785);
  
  var outbound = new nssocket.NsSocket();
  outbound.data(['you', 'there'], function () {
    outbound.send(['iam', 'here'], { iam: true, indeedHere: true });
  });
  
  outbound.connect(6785);

Reconnect Example

nssocket exposes simple options for enabling reconnection of the underlying socket. By default, these options are disabled. Lets look at a simple example:

  var net = require('net'),
      nssocket = require('nssocket');
  
  net.createServer(function (socket) {
    //
    // Close the underlying socket after `1000ms`
    //
    setTimeout(function () {
      socket.destroy();
    }, 1000);
  }).listen(8345);
  
  //
  // Create an NsSocket instance with reconnect enabled
  //
  var socket = new nssocket.NsSocket({
    reconnect: true,
    type: 'tcp4',
  });
  
  socket.on('start', function () {
    //
    // The socket will emit this event periodically
    // as it attempts to reconnect
    //
    console.dir('start');
  });
  
  socket.connect(8345);

API

socket.send(event, data)

Writes data to the socket with the specified event, on the receiving end it will look like: JSON.stringify([event, data]).

socket.on(event, callback)

Equivalent to the underlying .addListener() or .on() function on the underlying socket except that it will permit all EventEmitter2 wildcards and namespaces.

socket.data(event, callback)

Helper function for performing shorthand listeners namespaced under the data event. For example:

  //
  // These two statements are equivalent
  //
  someSocket.on(['data', 'some', 'event'], function (data) { });
  someSocket.data(['some', 'event'], function (data) { });

socket.connect(port[, host, callback])

Equivalent to the .connect() method of the underlying socket with additional error handling of the arguments passed

socket.end()

Closes the current socket, emits close event, possibly also error

socket.destroy()

Remove all listeners, destroys socket, clears buffer. It is recommended that you use socket.end().

Tests

All tests are written with vows and should be run through npm:

  $ npm test

Author: Nodejitsu

Contributors: Paolo Fragomeni, Charlie Robbins, Jameson Lee, Gene Diaz Jr.