node.js serialport在Windows上没有打开端口

Question

var SerialPort = require("serialport");
var port = new SerialPort("COM5");

port.on('open', function() {
  port.write('main screen turn on', function(err) {
    if (err) {
      return console.log('Error on write: ', err.message);
    }
    console.log('message written');
  });
});

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

install npm -g serialport 
install npm serialport

  

错误：打开COM5：未知错误代码121