Node.js server/client to connect to send and receive message

i have a sensor that connects to a router. I need to create something in node.js that can discover the ip of the sensor in the subnetwork and send a message to the sensor.

I am a bit confused.

I have this server written in node.js:

var udp = require('dgram');

// --------------------creating a udp server --------------------

// creating a udp server
var server = udp.createSocket('udp4');

// emits when any error occurs
server.on('error',function(error){
  console.log('Error: ' + error);
  server.close();
});

// emits on new datagram msg
server.on('message',function(msg,info){
  console.log('Mensagem recebida do cliente : ' + msg.toString());
  console.log('Recebido %d bytes de %s:%d\n',msg.length, info.address, info.port);

//sending msg
server.send('envio',info.port,'localhost',function(error){
  if(error){
    client.close();
  }else{
    console.log('Data sent !!!');
  }

});

});

//emits when socket is ready and listening for datagram msgs
server.on('listening',function(){
  var address = server.address();
  var port = address.port;
  var family = address.family;
  var ipaddr = address.address;
  console.log('Server is listening at port' + port);
  console.log('Server ip :' + ipaddr);
  console.log('Server is IP4/IP6 : ' + family);
});

//emits after the socket is closed using socket.close();
server.on('close',function(){
  console.log('Socket is closed !');
});

server.bind(2222);

// setTimeout(function(){
// server.close();
// },8000);

I have this client:

var udp = require('dgram');
var buffer = require('buffer');



// creating a client socket
var client = udp.createSocket('udp4');

//buffer msg
var data = Buffer.from('T');

client.on('message',function(msg,info){
  console.log('Mensagem recebida do server : ' + msg.toString());
  console.log('Recebido %d bytes de %s:%d\n',msg.length, info.address, info.port);
});

//sending msg
client.send(data,2222,'localhost',function(error){
  if(error){
    client.close();
  }else{
    console.log('Mensagem enviada:' + ' ' + data);
     //client.close();

  }
});

If i run the server and the client, they change messages.

I have this code that gives me the ip's in the subnetwork:

var fs = require('fs');

fs.readFile('/proc/net/arp', function(err, data) {
    if (!!err) return done(err, null);

    var output = [];
    var devices = data.toString().split('\n');
    devices.splice(0,1);

    for (i = 0; i < devices.length; i++) {
        var cols = devices[i].replace(/ [ ]*/g, ' ').split(' ');

        if ((cols.length > 3) && (cols[0].length !== 0) && (cols[3].length !== 0) && cols[3] !== '00:00:00:00:00:00') {
            output.push({
                ip: cols[0],
                mac: cols[3]
            });
        }
    }

    console.log(output);
});

In someway i can do what i want with this codes? Anyone have a tutorial or something that can help me?

via Miguel Coelho