Port Numbers

Provide foundation of open networking

Like a set of post office box numbers for the protocol

Each type of application gets a port number

Port number + host address gives it a unique identifier to send and receive

Over 65,000 valid port numbers

OS can support many applications at once

Warcraft : What ports need to be open?

In order to connect to Battle.net, connect to others over a Local Area Network, and allow others to connect to games you create, the following ports need to be opened.
Diablo, Warcraft II Battle.net Edition, and StarCraft:
* Ports 6112 through 6119 TCP & UDP