Port Numbers

• One computer can offer multiple services over the Internet
  • For example, both a web server program and an email server program
• When data are sent to that computer, they need to indicate which program is to receive the data
• IP uses port numbers for this
  • A port number is an integer between 0 and 65,535
  • The sending program must know the port number of the receiving program
  • This number is included in the transmitted data