This error message will only be displayed if you’ve ticked the check box “Always check that the port is opened”. This setting should be ticked by tech-savvy users only.
If you’ve ticked the check box, GigaTribe will refuse to connect unless a direct TCP connection can be established. This usually requires router, firewall and antivirus settings. This type of connection is refered as the direct connection. You can find instructions on how to use the direct connection mode.