Network Theory & Network Programming for Wireshark

Hello,

I am trying to learn to learn a packet sniffer and have started with libpcap tutorial.

Is learning networking OSI model ...with every layer & protocol in detail (theoretically) be advise able at this point or should I learn network theory and related protocols on the fly (as & when the requirement comes up) through books & RFCs.

Secondly, I also dont know network programming (Richard Stevens). Will it be advisable to learn that beforehand as well.

can someone help guide me with the appropriate path & approach that I should follow.

Regards,

Mohit