When I wanna join any of the servers(S2 Demo), there is always a messege"Did not receive guest info. Lost connection to the host". How can it be solved? 3x!!

Seeing that you are from China, its probably the connection. If you are trying to connect to servers to Europe, (where probably more than 80% of LFS servers are located) you will have a very high ping and/or get this message.

I'm now in Germany. And the ping is good(about 12s) with the servers which I wanna join. Is it possible that it has something to do with the ports of the network? I have allowed LFS in firewall. I dont know if I should open some ports to get the guest info.