How does TCP differ from UDP? What are the use cases?

TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) are two main transport layer protocols in a network.

Differences:

• Reliability: TCP provides reliable data delivery by establishing a connection, acknowledging receipt of packets, and retransmitting lost packets. UDP is connectionless and does not provide acknowledgments, so data can be lost.
• Order of delivery: TCP guarantees the order of packet delivery, UDP does not.
• Speed: UDP is faster due to the lack of control and acknowledgment mechanisms.
• Resource usage: TCP requires more resources because of connection and state management.

Use cases:

• TCP: web servers (HTTP/HTTPS), databases, email — where reliability and data integrity are important.
• UDP: video/audio streaming, online gaming, VoIP — where speed and latency are critical, and some packet loss is acceptable.

Example in Go for a TCP server:

ln, err := net.Listen("tcp", ":8080")
if err != nil {
    log.Fatal(err)
}
for {
    conn, err := ln.Accept()
    if err != nil {
        continue
    }
    go handleConnection(conn)
}

For UDP:

addr, err := net.ResolveUDPAddr("udp", ":8080")
conn, err := net.ListenUDP("udp", addr)
buf := make([]byte, 1024)
for {
    n, addr, err := conn.ReadFromUDP(buf)
    // data processing
}