how do the computer know which process is listening to which port?

hello guys,

i have a basic and maybe stupid question. how do the computer know which process is listening to which port.

for example i have several web browsers installed on my machine.

and if i run firefox and ie at the same time, can my html request sent from firefox be captured by ie?

i'm thinking of implementing a p2p forum system to deal with censorship. but if i choose to use some specific port, the system can be easily banned. but if i can use a port like 80, things could be better. after all, the government cannot ban all web browsing.

thank you.

You must differentiate between clients and servers.

A server listens to a well-known port, e. g. a web server usually listens to port 80. Each client that wants to connect to the server must know this port.

A client connects to that port, using a (randomly chosen) local port (that does not really matter).

Using 2 web browsers, like in your example, would lead to 2 connections, both completely independant.

A connection is uniquely defined by the 5-tupel
local-IP-address, local-port, remote-IP-address, remote-port, protocol.

You thus may have 2 connections
<your-local-IP-address>, 4000, <server-IP-address>, 80, TCP
and
<your-local-IP-address>, 4001, <server-IP-address>, 80, TCP
for your 2 browsers.

u can know which process is using which port...

use fport to kno...

here goes the link
http://techzonebyasit.blogspot.com/2008/07/fport.html