The following IP Ports and Protocols are excerpted from Networking Fundamentals.
Port number – Protocols name
20 – File Transfer Protocol (FTP) data
21 – File Transfer Protocol (FTP) control
23 – Telnet
25 – Simple Mail Transfer Protocol (SMTP)
53 – Domain Name Service (DNS)
80 – HyperText Transfer Protocol (HTTP)
110 – Post Office Protocol version 3 (POP3)
119 – Network News Transport Protocol (NNTP)
139 – NetBIOS Session Service
143 – Internet Message Access Protocol (IMAP)
161 – Simple Network Management Protocol (SNMP)
Common protocols include TCP, UDP and ICMP. There are actually a great number of protocols, but these three are the most prevalent. TCP is used to handle the underlying data streams for web, email, news and almost every other popular network application. That does not mean that UDP and ICMP are not important however.
While TCP is good at providing reliable, error-free data UDP is used for applications where speed or simplicity is more important that reliability. Applications like DNS lookups and SNMP use the UDP protocol. ICMP is used for untilities such as ping and traceroute. If you have ever seen the destination host unreachable message, this is ICMP in action.