This test is the basic prerequisite for all Network programming tests. You must be able to demonstrate that you can host a TCP 'server' and accept a connection from the Internet (aka, this web site).
If you are behind a firewall or a router, you will need to forward port 12345 (TCP) to your machine and allow a TCP connection to come to you from the internet. When you press the "I'm ready" button below, a connection will be made to your computer and then terminated - thus completing this test.