Send struct over socket in C

Question

I am developing a client/server program and my client has to send messages to the server.

Sample message C structure:

struct Reg         


        

Answer 1

sizeof(regn) gives size of your complete structure Registration, wheras sizeof(data) is size of pointer on your machine that is 4 bytes (data should be pointer of Registration type).

In expression:

memcpy(data, ®n, sizeof(regn));
        ^     ^
        |     value variable of struct type 
        is pointer

also notice in printf, . is used to access elements e.g. regn.multicastGroup.