I start up the Xulu system and everything looks OK, but after a few seconds I get the message: “Cannot connect to the Xulu server. Please check that your computer is connected to the internet and that you do not have a firewall blocking access.” What is going on?

The problem here is that your computer is not receiving communications from any other computers in the Xulu system. The most common reason is that your machine is behind a router or firewall that is blocking incoming communications. Anytime your computer receives incoming data, it is sent to a “port.” Your computer has many ports that can receive data, and different activities will utilize different ports. Most proxy servers, firewalls, and other Internet connection sharing methods can restrict port access. Your configuration may be restricting packets from “unknown sources.” In this case an “unknown source” would be defined as any IP address that you have not initiated the contact with. Once you contact the IP address, your proxy and/or firewall considers it “safe”, or a “known source”, since you initiated the contact. The Xulu system is more complicated, because your computer will receive communications form all other user computers. This becomes the real problem if your connection is restricting them from contacting you. Because there are so many network configurations available, there is no single solution to this. Some things you can try:

  • Are you running Windows Firewall? If so, make sure you allow access to the Xulu client application.
  • Is your router blocking access to incoming data? Make sure that you open up ports 2040-2168 for UDP incoming.
  • If your computer is behind a router or firewall, you can temporarily bypass this hardware (i.e. connect your computer directly to your modem or other internet access point) to verify that the Xulu system works properly.

You may need to contact your ISP or network administrator for assistance if you have opened the correct ports but still cannot connect or get others connected to you.

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