tcp/udp socket program

tcp-client.js

/**
 * tcp socket programming (client-side)
 * @author shj
 */

// import module
const net = require('net');

// create TCP socket
const client = new net.Socket();

// try make a connection to server (target: 127.0.0.1, port: 8888)
client.connect({ port: 8888, host: '127.0.0.1' }, () => { // when connected
  // print message
  console.log('connected to server');

  // send message to server
  client.write('hello server');

  // when server sends a message
  client.on('data', (chunk) => {
    // print message
    console.log('client got a message >> ', chunk.toString());
  });

  // when connection is over
  client.on('end', () => {
    // print message
    console.log('connection is over');
  });
});

tcp-server.js

/**
 * tcp socket programming (server-side)
 * @author shj
 */

// import module
const net = require('net'); // for tcp socket programming

// create TCP server
const server = new net.Server();

// listening for client connection (port: 8888)
server.listen(8888, () => {
  console.log('server listening...');
});

// when connected
server.on('connection', (sock) => { // get client socket
  // send message
  sock.write('connected with server');

  // when client sends a message
  sock.on('data', (chunk) => { // chunk: message(Buffer type)
    // print message
    console.log('server got a message >> ', chunk.toString());
  });

  // when connection is over
  sock.on('end', () => {
    // print message
    console.log('connection is over');
  });
});

udp-client.js

/**
 * udp socket programming (client-side)
 * @author shj
 */

// import module
const dgram = require('dgram');

// create client socket
const client = dgram.createSocket('udp4');

// create a message
const message = Buffer.from('message from client!');

// init target
const target = '54.146.216.8'; // AWS EC2 instance

// send message (msg, offset, length, port, address, callback)
client.send(message, 0, message.length, 33333, target, (err, bytes) => {
  // print message
  console.log(`send message: ${message}`);

  // close client socket
  client.close();
});

udp-server.js

/**
 * udp socket programming (server-side)
 * @author shj
 */

// import module
const dgram = require('dgram'); // for transport datagram packet

// create server socket
const server = dgram.createSocket('udp4');

// error handling
server.on('error', (err) => {
  // print error
  console.log(`server error with >>\n${err.stack}`);
  server.close(); // close server socket
});

// message handling
server.on('message', (msg, rinfo) => {
  // print message
  console.log(`server got a message >>\n${msg} from ${rinfo.address}:${rinfo.port}`);
});

// when init handling
server.on('listening', () => {
  // print message
  console.log('server listening...');
});

// start listening
server.bind(33333);