client port number

Question

I was wondering how to, using C, find out what port a client is currently listening to. ie, I want to know what the source port is, not the destination port.

Thanks in advance!

Answer 1

Not sure what you mean. Clients don't listen, servers do.

Answer 2

If you're talking about how to scan for all open ports, then you might be after a port scanner. There are many many many many source codes available but I definitely don't recommend you use one of them, they are usually slow even if multithreading is enabled. Why? There's nmap : http://nmap.org/

Answer 3

The socket address structure should be filled-in by the connect() system-call. Check it after a successful return from that call.

Answer 4

根据您想要的内容（我现在很难猜测），您想要调用getsockname（）或getpeername（）。