Simple Node Socket Server

server.js

const net = require('net');

const hostname = process.env.SERVER_HOSTNAME || '0.0.0.0';
const port = process.env.SERVER_PORT || 8124;
const interval = process.env.INTERVAL || 1000;
const plates = process.env.PLATES ? process.env.PLATES.split(',') : undefined;

const sockets = [];

const server = net.createServer((socket) => {
  const clientAddress = `${socket.remoteAddress}:${socket.remotePort}`;
  console.log(`new client connected: ${clientAddress}`);

  socket.on('data', data => {
    console.log(`Receive data: ${data}`);
  });

  socket.on('close', () => {
    const index = sockets.findIndex((o) => {
      return (o.remoteAddress === socket.remoteAddress) &&
        (o.remotePort === socket.remotePort);
    });
    if (index !== -1) sockets.splice(index, 1);
    console.log(`connection closed: ${clientAddress}`);
  });

  socket.on('error', (err) => {
    console.log(`Error occurred in ${clientAddress}: ${err.message}`);
  });

  sockets.push(socket);
}).on('error', (err) => {
  // Handle errors here.
  throw err;
});

setInterval(() => {
  sockets.forEach(socket => {
    const plate = generatePlate(); 
    socket.write(`${plate},https://dummyimage.com/600x400/32b85c/fff.jpg&text=${plate}` + '\n');
  });
}, interval);

server.listen(port, hostname, () => {
  console.log('opened server on', server.address());
});

const generatePlate = () => {
  if (plates) {
    const index = Math.floor(Math.random() * plates.length); 
    return plates[index];
  } else {
    return generateLetters(3).toUpperCase() + (Math.floor(Math.random() * (9999 - 1000 + 1)) + 1000)
  }
}

const generateLetters = (len) => {
  let text = '';
  const charset = 'abcdefghijklmnopqrstuvwxyz';
  for (let i = 0; i < len; i++) {
    text += charset.charAt(Math.floor(Math.random() * charset.length));
  }
  return text;
}

const randomInt = (min, max) => {
	return min + Math.floor((max - min) * Math.random());
}