code: function startRelay(portPair) {
    var devicePort = portPair[0]
      , relayPort = portPair[1];
  
    console.log('Starting relay from local port: %s -> device port: %s',
      relayPort, devicePort);
  
    new usbmux.Relay(devicePort, relayPort, {udid: argv.udid})
      .on('error', onErr)
      .on('warning', console.log.bind(console, 'Warning: device not found...'))
      .on('ready',      info.bind(this, 'Device ready: '))
      .on('attached',   info.bind(this, 'Device attached: '))
      .on('detached',   info.bind(this, 'Device detached: '))
      .on('connect',    info.bind(this, 'New connection to relay started.'))
      .on('disconnect', info.bind(this, 'Connection to relay closed.'))
      .on('close',      info.bind(this, 'Relay has closed.'));
  }
docs: Start a new relay from a pair of given ports
  @param  {integer[]} portPair - [devicePort, relayPort]