TCP pros and cons

• acknowledgment

• guaranteed delivery

• connection based

• congestion control

• ordered packets

• Larger packets

• More bandwidth since more headers.

• Slower (because of retransmission) than UDP

• Stateful (once connection is lost, cannot resume it).

• Server memory (DOS)

TCP code example

// server
const net = require('net');

const server = net.createServer((socket) => {
  socket.write('Hello.');
  socket.on('data', (data) => {
    console.log(data.toString());
  });
});

server.listen(8080);


// client using telnet, which can be installed by homebrew
telnet 127.0.0.1 8080

// client result
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
Hello.

UDP (user datagram protocol) pros and cons

• Horizontal Scaling

• No acknowledgment

• No guaranteed delivery

• connectionless

• No congestion control

• No ordered packets

• Lack of security (No connection, I don’t know who you are). Many firewalls disable UDP for this reason

• Smaller packets

• Less bandwidth

• Faster than TCP

• Stateless

UDP code example

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

socket.on('message', (msg, rinfo) => {
  console.log(`server got: ${msg} from ${rinfo.address}:${rinfo.port}`);
});

socket.bind(8081);