An in-depth guide on how to play private match with friends for IW4x.
Connecting to your friends:
Go to here and PM anyone who wants to join your IP Address.
Start IW4x and select 'CREATE GAME' from the main menu.
Click 'START GAME'.
Tell anyone who wants to join, open the console by using the tilde key while at the main menu.
Get them to enter the following command, replacing 'HostsIPAddress' with the IP you previously sent him: /connect HostsIPAddress:28960
Failed to join:
If you followed the above correctly and your friends are unable to join you or you are unable to join them, the host of the private match will need to port forward in order for them to connect to you or you connect to them.
Port Forward port "28960" UDP & TCP
You can find how to do this by Googling 'YourRouterName Port Forwarding'
Note: If port forwarding is too complex, just stick to playing public servers, or maybe join an empty server so you have the same experience as a private game.