test.js

var SerialPort = require("serialport").SerialPort
var serialPort = new SerialPort("/dev/ttyS0", {
    baudrate: 9600
});
serialPort.on("open", function() {
        serialPort.on('data', function(data) {
                console.log(data.toString())
        })
        var stdin = process.openStdin();

        stdin.addListener("data", function(d) {
            serialPort.write(d.toString()+'\n')
            console.log("you send: [" + d.toString().trim() + "]");
        });
})