[Posix UDP] What to consider when coding for the multithreaded udp server with thread pool

gistfile1.txt

1. The socket's file descriptor must be global(if you wanted to share the socket)
2. You must pass the sizeof the destination length(sizeof(client_addr)) into the thread in pthread_create as if you do not then you won't get a correct result as the client_addr is a pointer to sockaddr_in instead of sockaddr_in, so the return value of sizeof() won't be the one that we wanted