This article is from the Secure Sockets Layer Discussion List FAQ, by Shannon Appel SAppel@consensus.com with numerous contributions by others.
Theoretically SSL can transparently secure any TCP-based protocol
running on any port if both sides know the other side is using SSL.
However, in practice, separate port numbers have been reserved for
each protocol commonly secured by SSL -- this allows packet
filtering firewalls to allow such secure traffic through.
As of October 1998, SSL has the following port numbers reserved
with the Internet Assigned Numbers Authority (IANA), a part of the
Internet Engineering Task Force (IETF):
Keyword Decimal Description ------- ------- ----------- nsiiops 261/tcp IIOP Name Service over TLS/SSL https 443/tcp http protocol over TLS/SSL ddm-ssl 448/tcp DDM-SSL smtps 465/tcp smtp protocol over TLS/SSL nntps 563/tcp nntp protocol over TLS/SSL sshell 614/tcp SSLshell ldaps 636/tcp ldap protocol over TLS/SSL ftps-data 989/tcp ftp protocol, data, over TLS/SSL ftps 990/tcp ftp, control, over TLS/SSL telnets 992/tcp telnet protocol over TLS/SSL imaps 993/tcp imap4 protocol over TLS/SSL ircs 994/tcp irc protocol over TLS/SSL pop3s 995/tcp pop3 protocol over TLS/SSL