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Summary of problem; Clients get a timeout error, I may or may not get a disconnection message from some port above 50,000. The router, firewall, and Windows Firewall are set wide-open. I have tried everything I can think of and remain perplexed.

I'm running a 1.5.2 server for a couple friends, everything has been working for months just fine. However, this evening one of them lost connection and couldn't reconnect. Then the other re-logged to see if they had the same problem, and they did. Now neither of them can connect, but can connect to other servers just fine.

Sometimes, when they try to connect I will get a disconnect message with their IP and some huge port number, most of them above 60,000, some between 50k and 60k...but most of the time I don't even get that.

As I said in the summary; Windows Firewall is off, my software firewall is off, and my IP is set as the "DMZ" on our Linksys router.

I've also tried every combination of DMZ and port forwarding. I've tried other ports in drastically different ranges. I've tried rebooting and resetting everything (server, router, modem). I've tried running a completely vanilla server.

When I run an offsite port-scan the status of 25565 is not consistent. Twice it was open, every other time it has been closed or blocked.

I am at wit's end. The only thing I can fathom at this point is that my ISP is selectively blocking Minecraft packets to my IP, but I still think that's unlikely. Please help me find a plausible explanation, if not a solution.

Thanks!

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What operating system is the Minecraft server running on? The only thing I can think of is that you need to set-up a static IP address for your server. This site contains guides for doing so on Windows, but not Linux. –  Wipqozn Jul 13 '13 at 13:47
    
@Wipqozn He is running windows: "Windows firewall is off..." Also, I don't thing setting up a static IP address will help this situation. His server is obviously still visible to them. –  ReallyGoodPie Jul 13 '13 at 16:10
    
Do you have access to another computer running on the same network? And if so, is it running the same OS as the computer you're using at the moment? Attempt to run the server of this machine and see if your friends can connect. If so, your normal machines configurations may be "breaking" the server. IF not, it may be your router and port forwarding setup. I highly doubt your ISP would block Minecraft packets being transferred. –  ReallyGoodPie Jul 13 '13 at 16:17
    
@ReallyGoodPie Indeed, I am running Windows. –  Desolace Jul 13 '13 at 17:06
    
@ReallyGoodPie continued; Other machines on LAN can connect just fine, but I have not tried hosting from another machine-- I have no idea why. Thanks! P.S. I also doubt the ISP would block Minecraft, but the port scan results were most perplexing. –  Desolace Jul 13 '13 at 17:13
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1 Answer

Summary; Barefruit DNS-jacking is causing my IP to get/appear blocked.

Solution; Blocking packets with this destination at the firewall prevents the problem.

Description; Every couple of minutes something on my server is trying to connect to 92.242.140.2 on Port 3544 (UPD packets). This IP falls in a range owned by Barefruit Ltd, a company that turns DNS errors into advertising. When I block these packets, it's smooth sailing. But if I permit these packets to pass through, I get the problem as described in the question and a huge range of ports come back as blocked on a port scan.

As not all ISP's engage in this practice, it is important to note that I have Cox Communications at present.

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protected by fredley Mar 25 at 12:55

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