Serial port buffer unload test

serial.js

var SerialPort = require('serialport');
var port = new SerialPort('/dev/ttyUSB0', {
  baudRate: 4800
});

port.on('open', function() {
  port.write(new Buffer(256), function(err) {
    if (err) {
      return console.log('Error on write: ', err.message);
    }
    console.log('message written');
    
    console.log('Calling drain');
    port.drain(() => {
      console.log('Drain callback returned');
      // Now the data has "left the pipe" (tcdrain[1]/FlushFileBuffers[2] finished blocking).
      // [1] http://linux.die.net/man/3/tcdrain
      // [2] http://msdn.microsoft.com/en-us/library/windows/desktop/aa364439(v=vs.85).aportx
    });
  });
});

  // Open errors will be emitted as an error event
  port.on('error', function(err) {
    console.log('Error: ', err.message);
  });
});