Hello!

The purpose of the different ports is to assign each application its own communication port over a network without the risk of confrontation between different apps.Therefore your computer has almost 65000 virtual ports.To avoid confrontations the computer industry has standardised certain ports the so called 1024 ports (number 0-1023).Examples of these ports are 21(2121) for FTP 23(2323) for Telnet 25(2525) for SMTP-server 53(5353) for DNS 80(8080) for Webb and 665 to 669 for IRC.Gnutella already uses one of these 1024 ports namely 63(6346-6348).This means that every port between
0000 and 10231023 is standardised ports.However not every port number between those numbers are used by any app so today about 65000 virtual ports are beeing used by todays computers and their apps.

Notice!
In reality the ports are nothing more then a bit of programming code that tells which application each sended or recieved file belongs to.

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<img src="http://www.jordysworld.de/emoticons/blob16.gif">Sincerely Joakim Agren!