TCP vs UDP: Understanding the Differences

When building network applications, choosing between TCP and UDP is a fundamental decision that affects performance, reliability, and user experience.

TCP (Transmission Control Protocol)

TCP is a connection-oriented protocol that ensures reliable data delivery.

Key Characteristics

TCP Handshake

Client          Server
  |    SYN     |
  |----------->|
  |   SYN-ACK  |
  |<-----------|
  |    ACK     |
  |----------->|
  |  Connected |

UDP (User Datagram Protocol)

UDP is a connectionless protocol that prioritizes speed over reliability.

Key Characteristics

Comparison Table

When to Use TCP

When to Use UDP

Code Example: Python Sockets

TCP Server

import socket

server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server.bind(('localhost', 8080))
server.listen(5)

while True:
    client, addr = server.accept()
    data = client.recv(1024)
    client.send(b"Response")
    client.close()

UDP Server

import socket

server = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
server.bind(('localhost', 8080))

while True:
    data, addr = server.recvfrom(1024)
    server.sendto(b"Response", addr)

Conclusion

Choose TCP for reliability-critical applications and UDP when speed matters more than guaranteed delivery.