Node.js send file with pure socket (low level transfer)

client.js

var net = require('net');
var socket = new net.Socket();
socket.connect(5000, "127.0.0.1");
var fs = require('fs');
var path = require('path');

var packets = 0;
var buffer = new Buffer(0);
socket.on('data', function(chunk){
  packets++;
  console.log(chunk);
  buffer = Buffer.concat([buffer, chunk]);
});

socket.on('close', function(){
  console.log("total packages", packets);

  var writeStream = fs.createWriteStream(path.join(__dirname, "out.jpg"));
  console.log("buffer size", buffer.length);
  while(buffer.length){
    var head = buffer.slice(0, 4);
    console.log("head", head.toString());
    if(head.toString() != "FILE"){
      console.log("ERROR!!!!");
      process.exit(1);
    }
    var sizeHex = buffer.slice(4, 8);
    var size = parseInt(sizeHex, 16);

    console.log("size", size);

    var content = buffer.slice(8, size + 8);
    var delimiter = buffer.slice(size + 8, size + 9);
    console.log("delimiter", delimiter.toString());
    if(delimiter != "@"){
      console.log("wrong delimiter!!!");
      process.exit(1);
    }

    writeStream.write(content);
    buffer = buffer.slice(size + 9);
  }

  setTimeout(function(){
    writeStream.end();
  }, 2000);

});

server.js

var net = require('net');
var fs = require('fs');
var path = require('path');
var fileName = "escondidas.jpg";
var filePath = path.join(__dirname, fileName);

var server = net.createServer(function(client){
  var packages = 0;
  var totalBytes = 0;
  var readStream = fs.createReadStream(filePath, {highWaterMark: 16384});
  readStream.on('data', function(chunk){
    packages++;    
    var head = new Buffer("FILE");
    var sizeHex = chunk.length.toString(16);
    while(sizeHex.length < 4){
      sizeHex = "0" + sizeHex;
    }
    var size = new Buffer(sizeHex);
    console.log("size", chunk.length, "hex", sizeHex);
    var delimiter = new Buffer("@");
    var pack = Buffer.concat([head, size, chunk, delimiter]);
    totalBytes += pack.length;
    client.write(pack);
  });
  readStream.on('close', function(){
    client.end();
    console.log("total packages", packages);
    console.log("total bytes sent", totalBytes);
  });

  client.on('error', function(){
    console.log("error del cliente");
  });

  client.on('close', function(){
    console.log("terminó comunicación con cliente");
  });

});

server.listen(5000);

server.on('listening', function(){
  console.log("servidor escuchando");
});
server.on('error', function(err){
  console.log("error del servidor");
});