lib/bus.js
function source(message) {
  var ip = [];

  for (var i = 0; i < 4; i++) ip.push(message[i]);

  return ip.join('.');
}
function source(message) {
  var ip = [];

  for (var i = 0; i < 4; i++) ip.push(message[i]);

  return ip.join('.');
}
Return message sender IP address

@param  {Buffer} message
@return {String}