Summary

Windows Sockets Model

Process Communicating

• Process: program running within a host.
  • client process: process that initiates communication.
  • server process: process that waits to be contacted.
• Within same host: Communicate using inter-process communication.
• Different hosts: Communicate by exchanging messages.

• Sockets: The “door” through which a process sends/receives messages. It is the interface between the application process and the transport layer protocol (TCP/UDP).
  • 2 sockets involved: one on each side.

Addressing Processes

• Host device has unique 32-bit address, however many process can run on same host, so we need to identify which process to send message to.
• Identifier includes both IP address and port numbers on host.
• Example Port numbers:
  • HTTP server: 80
  • Mail server: 25
• To send HTTP message to siit.tu.ac.th web server:
  • IP Address: 128.119.245.12
  • Port number: 80