udp_client.js

var dgram    = require('dgram'),
    fs       = require('fs'),
    readline = require('readline');

var HOST = 'localhost';
var PORT = 4149;

//var client = dgram.createSocket('udp6');
var client = dgram.createSocket('udp4');
client.bind(0);

client.on('message', function (msg, rinfo) {
  console.log('Received: ' + rinfo.address + ':' + rinfo.port + ': ' + msg);
});

function transmit(message) {
  var buffer = new Buffer(message);

  client.send(buffer, 0, buffer.length, PORT, HOST,
    function(error, bytes) {
      if (error) throw error;
      console.log('Sent to:  ' + HOST + ':' + PORT);
    }
  );
}

var filename = process.argv[2];
if (! filename) filename = '/dev/stdin';

var input = readline.createInterface({
  input:    fs.createReadStream(filename),
  output:   process.stdout,
  terminal: false
});

input.on('line', function(line) {
  transmit(line + ' ');
});

input.on('close', function() {
  client.close();
});