node.js listen for UDP and forward to connected http web clients

Question

I'm new to node.js, so forgive the ignorance if this is simple.

What I want to do is setup a simple node.js http server to which a web-client connects. I also want the node.js server to act as a UDP listener on a separate port, on which it will receive JSON payloads from some other application. I want the node.js server to then forward these JSON payloads immediately to one or more of the connected web-clients.

I got this far from some initial googling around:

1. Create a simple node.js http server that responds with a static html page:

   //Initialize the HTTP server on port 8080, serve the index.html page
   var server = http.createServer(function(req, res) {
       res.writeHead(200, { 
           'Content-type': 'text/html'});
           res.end(fs.readFileSync(__dirname + '/index.html'));
       }).listen(8080, function() {
           console.log('Listening at: 127.0.0.1 8080');
       }
   );
   

2. Initialize a UDP server on a separate port:

   //Initialize a UDP server to listen for json payloads on port 3333
   var srv = dgram.createSocket("udp4");
   srv.on("message", function (msg, rinfo) {
     console.log("server got: " + msg + " from " + rinfo.address + ":" + rinfo.port);
     io.sockets.broadcast.emit('message', 'test');
     //stream.write(msg);
     //socket.broadcast.emit('message',msg);
   });
   
   srv.on("listening", function () {
     var address = srv.address();
     console.log("server listening " + address.address + ":" + address.port);
   });
   
   srv.bind(5555);
   

3. Use socket.io to establish a live connection between web-client and server:

   //this listens for socket messages from the client and broadcasts to all other clients
   var io = require('socket.io').listen(server);
   io.sockets.on('connection', function (socket) {
       socket.on('message', function (msg) {
         console.log('Message Received: ', msg.data.skeletons[0] ? msg.data.skeletons[0].skeleton_id : '');
         socket.broadcast.emit('message', msg);
       }
     );
   });
   

I guess my problem is I don't know how to bridge 2 and 3, to get the received UDP packets broadcasted to the connected socket.io clients. Or perhaps there's a simpler, more elegant way of doing this? I found the documentation for socket.io to be lacking...

EDIT: thanks to the person that fixed the code formatting

Answer 1

I made a running example for you to get going with: http://runnable.com/UXsar5hEezgaAACJ

For now it's just a loopback client -> socket.io -> udp client -> udp server -> socket.io - > client.

here's the core of it:

var http = require('http');
var fs = require('fs');
var html = fs.readFileSync(__dirname + '/index.html');

//Initialize the HTTP server on port 8080, serve the index.html page
var server = http.createServer(function(req, res) {
  res.writeHead(200, { 
    'Content-type': 'text/html'
  });
  res.end(html);
}).listen( process.env.OPENSHIFT_NODEJS_PORT, process.env.OPENSHIFT_NODEJS_IP, function() {
  console.log('Listening');
});

var io = require('socket.io').listen(server);

io.set('log level', 0);

io.sockets.on('connection', function (socket) {
  socket.emit('message', 'connected');
  socket.on('message', function (data) {
    console.log(data);
    var address = srv.address();
    var client = dgram.createSocket("udp4");
    var message = new Buffer(data);
    client.send(message, 0, message.length, address.port, address.address, function(err, bytes) {
      client.close();
    });
  });
});

var dgram = require('dgram');

//Initialize a UDP server to listen for json payloads on port 3333
var srv = dgram.createSocket("udp4");
srv.on("message", function (msg, rinfo) {
  console.log("server got: " + msg + " from " + rinfo.address + ":" + rinfo.port);
  io.sockets.emit('message', 'udp');
});

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

srv.on('error', function (err) {
  console.error(err);
  process.exit(0);
});

srv.bind();