Implementing UDP on Espruino, Using UDP broadcast to find server IP.

You can do both UDP and TCP at the same time.

Wifi.at.cmd("AT+CWMODE_CUR=3\r\n", 1000, function(d){console.log(d+"xx1");});

You call SetUDP and then setup a network with protocol 17 for UDP.
Then you call SetTCP and setup either HTTP or a TCP network.

     wifi.SetUDP();
     var client = require("net").connect({host: BroadIP, port: UDPport,protocolVersion: 17}, function() {

Use the UDP to obtain the IP address of the server and then

          wifi.SetTCP();
           getReply(console.log);
...
function getReply(callback) {
  var options = {
    host: ServerIP,
    port: '8080',
    path:"/",
    method:'GET',
    headers: {
    }
  };
  console.log("getReply");
  require("http").request(options, function(res)  {
    var d = "";
    res.on('data', function(data) { d+= data; });
    res.on('close', function(data) {
      var j = JSON.parse(d);
      console.log("d= ",d);//console.log("j= ",j);
      if (callback) callback((j&&j.result)?j.result:undefine­d);
    });
  }).end();
}//end getReply

On the server side

    wifi.SetUDP();
  var client = require("net").connect({host:BroadIP,por­t:UDPport ,protocolVersion: 17}, function() {
    console.log('client connected');
    client.write(JSON.stringify(UDP1));
    client.on('data', function(data){
     ddata+=data;
     if(ddata.charAt(ddata.length-1)==='}'){
      UDP2=JSON.parse(ddata);
      console.log(">"+ddata);
      if(UDP1.ServerName===UDP2.ServerName){
       UDP2.ServerIP=UDP1.ServerIP;
       client.write(JSON.stringify(UDP2));
       ddata="";
      }//endif
     }//endif
    });//end client on data
    client.on('close',function(){console.log­("client Close");});
    client.on('end', function() {
     console.log('client disconnected');
    });//end client on end
    //client.end();
   });//end UDP client connect
});//end wifi.getIP
//HTTP or Network Server goes here
   wifi.SetTCP();
serveHTML();
//////////////////
.....
function serveHTML(){
var http=require("http").createServer(onPage­Request).listen(8080);
}//end serveFile


function onPageRequest(req, res) { 
//console.log("Req= ",req);
//console.log("Header",req.headers);
if (req.method=="POST") {
  console.log("Post");
  doPost(req,res);
}else{
  doGet(req,res);
}//endif
}//end on PageRequest