TCP Port Numbers

• Like UDP, TCP uses 16-bit port numbers to address applications

• Also like UDP, TCP servers typically listen to a “well known” port

• • This way, client applications don’t need to dynamically look up destination port numbers
  • Most but not all well-known server ports are <1024
  • Examples: Telnet (23), FTP (21), HTTP (80)

• Like UDP, most TCP clients choose an “ephemeral” port