Common TCP Application And Server Port Assignments (Ports)

Interactive session-based protocol. Requires the connection-based nature of TCP.

The classic example of a TCP-based messaging protocol.

An example of a protocol that uses both UDP and TCP. For simple requests and replies, DNS uses UDP. For larger messages, especially zone transfers, TCP is used.

E-mail message retrieval protocols; use TCP to exchange commands and data.

Used to send large files, so ideally suited for TCP

Used for transferring NetNews (USEnet) messages, which can be lenghy

Uses an exchange of commands, and sends possibly large files between devices

Another email message retrieval protocol

A messaging protocol that has been largely replaced by the WWW.

While interior routing protocols like RIP and OSPF use either UDP or IP directly, BGP runs over TCP. This allows BGP to assume reliable communication even as it sends data over potentially long distances.

NFS was originally implemented using UDP for performance reasons. Given that it is responsible for large transfers of files and UDP is unreliable, this was probably noot the best idea, and TCP versions were created. The latest version of NFS uses TCP exclusively.

IRC is like Telnet in that it is an interactive protocol that is strongly based on the notion of a persistent connection between a client and server.

Used for the X Windows graphical system. Multiple ports are dedicated to allow many sessions.

A session protocol, clearly better suited to TCP than UDP.