You're talking about network programming. You send packets through sockets in C, which allows you to setup a client-server interface. Here is a good tutorial on sockets.
Next time try googling around before asking a question; googling for "packets" would have brought up a wealth of information that would have answered your question.
John A
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John A
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Perhaps there's not better place than to learn than from the creator of the language, that is, Bjarne Stroustrap.
Small correction, those are not written by Bjarne Stroustrup. Good books though.
WolfPack
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