C++ Winsock API how to get connecting client IP before accepting the connection?

Question

I am using the Winsock API (not CAsyncSocket) to make a socket that listens for incoming connections.

When somebody tries to connect, how can I get their IP address

Answer 1

accept the connection, look at the IP, if it is not allowed, close the connection

Edit:

I'm assuming you're talking about TCP connection. When you listen to the port and a connection comes from a client, the API will perform the TCP 3-way handshake, and the client will know that this port is being listened to.

I am not sure if there is a way to prevent sending any packets (i.e. accepting the connection) so that you can look at the IP address first and then decide.

The only way I can think of is to do packet filtering based on the source IP at the network layer (using firewall, for example).