Using UPD to find IP addresses for a TCP network in 5 parts.

1. Use UDP to allow clients to find the server IP address
   The UDP is used with a broadcast IP to allow a named client to locate a named server’s IP address.
   The message sent via UDP:

   function UDPmsg(a,b,c,d){
   this.ClientName=a;
   this.ClientIP=b;
   this.ServerName=c;
   this.ServerIP=d;
   }
   var UDP1=new UDPmsg("Bob",0,"Bill",0);
   

Client named Bob will ask server named Bill for Bill’s IP address

The server code:

//UDP_TCPserver1.js
//2 Oct 2016
//espruino board with ESP8266
//PICO  with ESP8266
//var BroadIP="255.255.255.255";
var BroadIP="192.168.1.255";
//var Hardware=0; //Espruino board
var Hardware =1; //PICO
var SSID="ssid";
var key= "router passcode";
var Serial;
var Wifi;
//var LocalIP;
var UDPport=1234;
var TCPport=9988;
function UDPmsg(a,b,c,d){
 this.ClientName=a;
 this.ClientIP=b;
 this.ServerName=c;
 this.ServerIP=d;
}
var UDP1=new UDPmsg("Bob",0,"Bill",0);
var UDP2=new UDPmsg("",0,"",0);
var ddata="";
function test(){
if(Hardware===1)Serial=Serial2;
if(Hardware===0)Serial=Serial4;

if(Hardware===1){
 digitalWrite(B9,1); // enable on Pico Shim V2
 Serial.setup(115200, { rx: A3, tx : A2 }); //Pico
}
if(Hardware===0)Serial.setup(115200, { rx: C11, tx : C10 }); 
//espruino board

console.log("Start connection process");
var wifi = require("UDP").connect(Serial, function(err) {
//var wifi = require("ESP8266WiFi_0v25").connect(Seri­al, function(err) {
  if (err)return 1;// throw err;
  Wifi=wifi;
console.log("Reset the ESP8266");
  wifi.reset(function(err) {
    if (err)return 1;// throw err;
Wifi.at.cmd("AT+CWMODE_CUR=3\r\n", 1000, function(d){console.log(d+"xx1");});
Wifi.at.cmd("AT+CIPMUX=1\r\n", 1000, function(d){console.log(d+"xx2");});
 console.log("Connecting to WiFi");
 wifi.connect(SSID,key, function(err) {
  if (err)return 1;//throw err;
  wifi.getIP(function(l,ip){
   console.log("IP= ",ip,"\n\r");
   UDP1.ServerIP=ip;
   console.log("LocalIP= ",UDP1.ServerIP);
   console.log("WiFi Connected ");

//start the UDP listener
   setupUDP(); 
//HTTP or Network Server goes here
   TCPserve();

////////////////////////////////////////­////////////////////
     });//end wifi.getIP
    });//end wifi.connectSSID
  });//end wifi.reset
});//end wifi.connect
}//end test

function setupUDP(){
    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 setupUDP

function TCPserve(){
 var data;
 Wifi.SetTCP();
 var server = require("net").createServer(function(c) {
  // A new client as connected
//  c.write("Hello");
/*  c.on('data', function(data) {
    console.log(">"+JSON.stringify(data));
  });
*/
   c.on('close',function(d){
   console.log("Close "+d);
   data=c.read(c.available());
   console.log(data);
   c.write(data);
     if(data==="LED Off"){
      digitalWrite(B12,0); //B12 is green LED
     }
     if(data==="LED On"){
      digitalWrite(B12,1);
     }
  });
  c.end();
});
server.listen(TCPport);
}//end TCPserve

var x;
console.log("Start");
x=test();
if(x!==0)console.log("Try again");//error seen

if(x===0) console.log("Exit Seen");

The output as the server starts

>echo(0);
Start
Start connection process
Try again
=undefined
Reset the ESP8266
Connecting to WiFi
OKxx1
OKxx2
IP=  192.168.1.3
LocalIP=  192.168.1.3
WiFi Connected
Client
Server
client connected
Send 0 {"ClientName":"Bob","ClientIP":0,"Server­Name":"Bill","ServerIP":"192.168.1.3"}
>

Again disconnect the server from WebIde and connect to Putty terminal application.

1 Attachment

• UDP_TCPserver1.js