socket-transport

Transport implementation over Node.js socket using JSON serialization. Fast and simple, perfect as communication channel between local or remote nodes.

Read about the Transport concept below.

Usage

npm install -s socket-transport

Server

const net = require('net');
const SocketTransport = require('socket-transport');

const server = net.createServer();
server.on('connection', socket => {
  console.log('incoming connection');
  const transport = new SocketTransport(socket);
  transport.on('message', message => {
    console.log('message: %j', message);
  });
  transport.on('close', err => {
    console.log('connection closed');
  });
  transport.send({
    foo: 'bar',
  });
});
server.listen(3000);

Client

const SocketTransport = require('socket-transport');

SocketTransport.connect({
  port: 3000,
  host: 'localhost',
}, (err, transport) => {
  if (err)
    return console.log(err.message);
  console.log('connected');
  transport.on('message', message => {
    console.log('message: %j', message);
  });
  transport.on('close', err => {
    console.log('connection closed');
  });
  transport.send({
    cat: 'meow',
  });
});

SocketTransport API

For details and other methods see common transport interface below

const SocketTransport = require('socket-transport');

Properties

socket

Reference to the socket passed to the constructor.

Methods

constructor(socket)

Takes Node.js socket to attach on.

send(message, callback)

From version 1.0.0

In Socket transport implementation it is possible to pass a callback as a second argument. Callback will be passed directly to socket.write() function and called when the message was actually sent. Also, send() returns the write status from socket.write(). Read more in Node.js docs.

Static

SocketTransport.connect(options, callback)

From version 2.0.0

options passed directly to the net.createConnection() Node.js function. Returns Node.js socket.

SocketTransport.MAX_BUF_LENGTH

Maximum incoming message size in bytes, defaults to 65536.

Concept

Transport is an abstraction layer providing uniform interface for message exchange. Message is a plain JavaScript object, and transport knows how to send it to the other party and receive from.

Uniform interface lets you write your application logic once and support different protocols or communication channels simultaneously or even switching them on the fly. After all, it's just a simple API for network messaging.

Transport interface

Transport class exposed by requiring module directly, sush as require('socket-transport').

Events

'message'

message - received message, javascipt object

Emitted when a new message is received.

'close'

err - Error object or null

Emitted when underlying system (and the transport itself) has been closed. Property open will become false right before the event. If transport was closed due to error, that error will be passed as err.

Properties

open

Boolean, describes transport is opened or not.

Methods

constructor(...)

Creates transport using some underlying system, such as TCP-socket or WebSocket. Arguments is to be specified in the specific transport implementation.

detach()

Detaches transport from the underlying system, making it possible to reuse it with other transports (for protocol switching on the fly, for example) or something else. Returns the underlying system object, passed to the constructor.

send(message)

message - javascript object to send

Sends a message to the other party using some kind of serialization. Sending a message with closed transport does nothing.

close(err)

Closes underlying system, making the transport a subject for garbage collection. Property open will become false immediately and event close will be emitted asynchronously after it has been closed. Optional parameter err will be passed to close event (available from version 1.0.0). Calls to close() may or may not emitting close event when the transport is already closed.

Static

connect(options, callback)

options - some options for connecting, depends on implementation
callback - should take parameters (err, transport)

Creates a client connection using options and invokes callback with null, transport when it's done, or just an err if connection fails. Returns an underlying system object.