How to listen tcp/ip port value in my windows application form

Question

Hi all,

Here i am connected one Access card machine(like our company id card which we are showing infront of door to open) to my computer through tcp/ip with port number 4370 and ip address is 192.168.1.1.

Now how to write an event to listen the port and get the card number ?
or how to write an event when that port gives a new number?

thank you

its very urgent........