Port Numbers and the Client/Server Model THERE ARE NOW MANY "SERVICES" AVAILABLE ON THE INTERNET. - WEB SERVERS, FTP SERVERS, MAIL SERVERS... "SPECIAL" PROGRAMS RUN ON SERVER MACHINES WAITING FOR NETWORK MESSAGES REQUESTING SERVICES. PROTOCOL STANDARDS SPECIFY PORTS FOR COMMON SERVICES (MAIL=25, FTP = 21, FINGER = 79, HTTP = 80) A CLIENT PROGRAM SENDS A REQUEST MESSAGE TO THE SERVER'S ADDRESS AND "WELL-KNOWN" PORT NUMBER. EACH CLIENT REQUEST INCLUDES A RETURN ADDRESS (IP ADDRESS + PORT NUMBER). SERVER SENDS REPLY TO RETURN ADDRESS.

The Web: Technologies and Techniques Links to other course pages: CS 105 Home Page CS 105 Lecture Schedule CS 105 On-line Discussion Group: All discussions Discussion relating to this lecture topic Williams College Department of Computer Science

This page is part of a section of lecture slides related to " The User Datagram Protocol & Ports " within the topic "The Internet Protocol Suite". Other slides within this section and other sections of slides for the topic "The Internet Protocol Suite" can be accessed using the links below. The Internet Protocol Suite TCP/IP = The Internet Protocol Suite The User Datagram Protocol & Ports Port Numbers and UDP Port Numbers and UDP (cont.) Port Numbers and the Client/Server Model Implementing UDP The Transmission Control Protocol Reliability Best-effort Delivery Router Congestion TCP TCP Implementation TCP Efficiency TCP as Internet Transport Protocol The Domain Name Service Domain Names Domain Name Servers Reliability and Retransmission A Reliable Delivery Problem Cautious Generals Solving the General's Problem Connections (Virtual Circuits)