The fact you can't connect to that test page is a sign port 6346 is blocked for you. It's either due to your LAN network or school deciding to block ports used for p2p sharing.

Try some other port numbers. Go to LW's menu Tools>Advance>Firewalls & change the listening port to something else. Here's some suggestions: 3500, 1203, 20282, 80. Don't forget to press apply button after changing the port no. & trying out each one. Also, go to your LW menu File>Connect & give it some time to connect. Even up to 30 mins.

There's a port test page you can use but you need to have LW open at that time (simultaneously.) And I think you also might need to have that port entered as LW's listening port before you should do the test. Try here & enter the port no.: http://home.no.net/tgrumpy/ct/dex.php