Introduction to Socket Programming

1
Introduction to Socket Programming

• Yen-Nien Wu
• CSIE, NTU

2
Outline

• Background
• What is a socket?
• TCP vs. UDP
• Byte Ordering
• Socket I/O
• TCP/UDP Client and Server
• I/O multiplexing
• HW 1 Web Proxy

3
Server and Client
Server and Client exchange messages over the
network through a common Socket API
Clients
Server
ports
user space
TCP/UDP
TCP/UDP
kernel space
Socket API
IP
IP
Ethernet Adapter
Ethernet Adapter
hardware
4
User Datagram Protocol(UDP) An Analogy

• Postal Mail
• Single mailbox to receive messages
• Unreliable ?
• Not necessarily in-order delivery
• Each letter is independent
• Must address each reply

• Postal Mail
• Single mailbox to receive letters
• Unreliable ?
• Not necessarily in-order delivery
• Letters sent independently
• Must address each reply

• UDP
• Single socket to receive messages
• No guarantee of delivery
• Not necessarily in-order delivery
• Datagram