Copyd from Beto's jj2 faq

"Q: I time out every time I connect to a server!

A: Argh… I hate that question, many people asked it to me like 70 times.

Well, it can be that you have a firewall blocking 10052 port on TCP and UDP which makes you to time out of the game every 30 seconds.

In fact just disable your firewall or open these ports to host and play:

Open 10052 and 10054 on TCP and UDP Inbound and Outbound.

If you’re behind a network and can’t host and play then open the same ports for your computer
"