How to block IP address in Windows 7 on custom packet reception

I want to detect the custom packet with signature. How to detect the packets? How to extract the packet data body so that I can verify the encrypted signature in the packet. Then I will have to give Full permission for one of my data in the server. What applications are there to perform the said activity already? If I have to automate this, which is the best approach? How to start with networking programming? I know the basics and your kind support towards this will help me in completing this objective.