Port Numbers

A port number is a number assigned to a service. You can think of an IP address and a port number like a street address and an apartment number. If you have ever lived in an apartment, then you know that everyone in the apartment complex has the same street address. So what tells the mail carrier where to put everyone s mail? The apartment number does. If it weren t for the apartment number then once the mail got to your street address all organization would end. You would have to search through everyone s mail to find yours. This is the same concept behind IP addresses and port numbers. The port number is used by a particular service. When a request is made the port number tells the computer which service it wants to talk to. You could say that the port number defines the endpoints of our connection. The format for using port numbers is the IP address followed by a colon and the port number. For example, let s say that we wanted to connect to the IP address 10.10.10.10 and we wanted to use the port for HTTP (port 80). The syntax would be 10.10.10.10:80. There are three categories of ports:

• Well-Known Ports

• Registered Ports

• Dynamic/Private Ports

The Internet Corporation for Assigned Names and Numbers (ICANN) is responsible for managing port numbers. The well-known port numbers range from 0 to 1023. The registered port numbers range from 1024 to 49151. The dynamic and private ports range...