connection.js

module.exports = Connection;

var util = require('util');
var Socket = require('net').Socket;
var MAGIC = 'VT01';

util.inherits(Connection, Socket);

function Connection() {
  Socket.call(this);
  this.on('readable', this._readPacket.bind(this));
}

Connection.prototype.send = function(data) {
  // encrypt
  if (this.sessionKey) {
    data = require('steam-crypto').symmetricEncrypt(data, this.sessionKey);
  }
  
  var buffer = new Buffer(4 + 4 + data.length);
  buffer.writeUInt32LE(data.length, 0);
  buffer.write(MAGIC, 4);
  data.copy(buffer, 8);
  this.write(buffer);
};

Connection.prototype._readPacket = function() {
  if (!this._packetLen) {
    var header = this.read(8);
    if (!header) {
      return;
    }
    this._packetLen = header.readUInt32LE(0);
  }
  
  var packet = this.read(this._packetLen);
  
  if (!packet) {
    this.emit('debug', 'incomplete packet');
    return;
  }
  
  delete this._packetLen;
  
  // decrypt
  if (this.sessionKey) {
    packet = require('steam-crypto').symmetricDecrypt(packet, this.sessionKey);
  }
  
  this.emit('packet', packet);
  
  // keep reading until there's nothing left
  this._readPacket();
};