client.js

// Usage:
// node client.js <server host> <server port> <size1> <size2> <byte>
// size1 - size of the first packet to send
// size2 - size of the second packet to send
// byte - fill packets with this byte (0x0 - 0xFF), default is random bytes

const net = require('net');
const crypto = require('crypto');

const host = process.argv[2];
const port = +process.argv[3];
const size1 = +process.argv[4];
const size2 = +process.argv[5];
const byte = +process.argv[6];

const socket = new net.Socket();
socket.connect(port, host, () => {
  let received = 0;

  console.log(`connected to ${host}:${port}`);

  const packet1 = isNaN(byte) ? crypto.randomBytes(size1) : Buffer.from(Array(size1).fill(byte));
  const packet2 = isNaN(byte) ? crypto.randomBytes(size2) : Buffer.from(Array(size2).fill(byte));

  socket.write(packet1);
  setTimeout(() => socket.write(packet2), 100);

  const heartbeat = setInterval(() => {
    console.log(`[<] ping`);
    socket.write('ping');
  }, 1000);

  socket.on("data", buffer => {
    const data = buffer.toString();

    console.log(`[>] [${++received}] ${data}`);
  });

  socket.on('error', (error) => {
    console.error(error);
  });

  socket.on('timeout', () => {
    socket.destroy();
  });

  socket.on('close', () => {
    clearInterval(heartbeat);
    console.log(`disconnected`);
  });
});