how to get the tcp header of a received packet in socket programming?

[esolve]

I want to get the TCP header of each received TCP packet (destined for a specific program,namely, a port)
it seems not possible to use recv() or recvfrom() to get the TCP header using regular socket.

So, I want to use raw socket
with raw socket, I can use recvfrom() to receive all IP packets destined to the host
if the host receives a lot packets,
I need to check the port number of each packet so see whether it is the needed.
then it could be very time and CPU comsuming?

while（）
{
recvfrom();
check_port_number();
}

are there any good ways to get the tcp header of a received tcp packet?

[kbw]

The sockets library's purpose is to hide all that stuff from you. You need to act as a sniffer to see the stuff you're interested in (or use a different networking library).

If you want to act as a sniffer, use libpcap. You can intelligently filter waht you see.