What Port Number Does an Application use?

Always asked question when configuring TCP/IP security of some sort.

TCP and UDP use port numbers from 0 - 65535 (16-bit) to identify an application.  The IANA or Internet Assigned Numbers Authority maintains a list at [http://www.iana.org/assignments/port-numbers] which describes which port number is used by an application.

The port numbers are divided into three ranges: the Well Known Ports, the Registered Ports, and the Dynamic and/or Private Ports.

• The Well Known Ports are those from                        0 through 1023.              Well Known Ports are assigned by the IANA
• The Registered Ports are those from                         1024 through 49151        The Registered Ports are listed by the IANA
• The Dynamic and/or Private Ports are those from   49152 through 65535

Below you can click to see a capture of an HTTP packet clearly showing that it is using port 80.

Here is a couple of tables with some common Port Numbers you may need to know.

 If you wish to see the whole list then visit - Port Numbers at http://www.iana.org/assignments/port-numbers...

I hope this all helps?

Matt Rowston

KB Keywords:  TCP/IP, IP, Protocol Number, Firewall, packet filter, ICMP Type Numbers.