Commonly Used Port Numbers

From time to time you may want to test a protocol or service from the command line. To do that, you may need to know the standard port number for that protocol. For example, you might want to verify that your SMTP server is accessible from the Internet. Testing the connection with a standard mail client might mean creating a new mail profile, which is a bother. Moreover, if the connection fails, you might not be able to see where or why it failed. By connecting with a terminal program to a specific port, you can manually send SMTP commands and verify the responses.

Below is a list of common protocols and their more-or-less “standard” port numbers.

	Telnet: Port 23		FTP: Port 21		SMTP: Port 25
	POP3: Port 110		HTTP: Port 80		NNTP: Port 119
	rtelnet: Port 107		TFTP: Port 69		Gopher: Port 70
	Finger: Port 79		Whois: Port 43		IRC: Port 194
	LDAP: Port 389		SNMP: Port 161		UUCP: Port 540
	Terminal Services/RDP: Port 3389		SQL Server: Port 1433		POP SSL: Port 995

The complete list of standard port numbers may be found in RFC1700:
http://www.faqs.org/rfcs/rfc1700.html