Logging udp-messages to a file with node.js

udp-server.js

var dgram = require("dgram");
var fs = require('fs');

var server = dgram.createSocket("udp4");
var messageToSend = new Buffer("A message to send");

server.on("message", function (msg, rinfo) {
  var stream = fs.createWriteStream("udp-stream.log", {'flags': 'a'});
  stream.once('open', function(fd) {
    stream.write("From "+rinfo.address+":"+rinfo.port+"\n"+msg+"\n");
  });


});

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

server.bind(4711);