If that test doesn't work, it means that LW's default port is blocked. I wonder why it's blocked? Sometimes ISPs block certain ports, sometimes ports are blocked by schools, it's a bit hard to guess why yours is blocked.

You could try changing to a higher port, one in the range of 49152 - 65535. Tools > options > advanced > firewall config, you'll see LW's listening port. If you did change listening port, you'd have to change port numbers allowed within a software firewall & also any ports forwarded through a modem/router. All port numbers would have to be the same.