Well at least we've ascertained that the normal port LW uses to connect through is blocked. The question is whether it's blocked due to your wireless system or by the ISP.

Most wireless connections use a NAT firewall. That probably needs looking at. Is it possible to contact your ISP to ask why port 6346 is blocked & whether it's the equipment or them that's blocking it? If it's the equipment, then ask them how to unblock it. They have no reason to block it other than being miserly & restricting your service to simply browsing. As for the equipment, I presume they provided it, so they should know how to solve the issue.

In the meantime, try a different port in LW. Go to LW's menu bar, Tools>Options>Advanced>Firewalls & change the setting from UPnP to manual port forwarding. Then change both the connection port AND the listening port to another, but they should be the same. Here's some port numbers you can try: 64049, 1111, 3500, 4008, 1203, 10000, 15189, 80, 20282, 22817, 443, 427, 34599, 40475, 49152, 6295, 25079.

After changing the ports numbers, press apply button. Then go to LW's menu bar, File>Disconnect. Wait a minute, then File>Connect. Give each one at least 20 mins to try to connect. Good luck!