udp-server.js

var dgram = require("dgram");
var fs = require("fs");
var stream = fs.createWriteStream("received.json",{ flags: 'w',
  encoding: "utf8",
  mode: 0666 });

var server = dgram.createSocket("udp4");
server.on("message", function (msg, rinfo) {
  console.log("server got: " + msg + " from " +
    rinfo.address + ":" + rinfo.port);
    stream.write(msg);
});

server.on("listening", function () {
  var address = server.address();
  console.log("server listening " +
      address.address + ":" + address.port);
});

server.bind(41234);
// server listening 0.0.0.0:41234