You probably came to this article, because you saw this error message:
Internal Exception: java.io.IOException: An existing connection was forcibly closed by the remote host.
This error message can be related to network connection issues from your computer to the Minecraft server. This issue is hard to find and even harder to fix since it can be caused by any network provider on that long way between your computer and the server. Often this might just be a temporary issue and fixes itself after some time.
If that's not the case the best you can do is running a traceroute and passing the output to Aternos and to your ISP. A traceroute tracks the connection from your computer to a remote server (Aternos) and outputs useful information to find problems with that connection. Running a traceroute does not fix the problem, instead it collects troubleshooting information that can help us to identify the cause of the problem.
This is an easy step-by-step guide about how to do a traceroute: https://www.wikihow.com/Traceroute
To determine connection problems to Aternos, run a traceroute to your servers Dyn-IP.
You can see the Dyn-IP by clicking the connect button on the server page. Please ignore the double dot and anything that follows. Example: If your servers Dyn-IP is
cat.aternos.host:25565 do a traceroute to
- The output of your traceroute as described above (ideally as screenshot and text)
- Your servers Dyn-IP
- Your public IP address, you can determine it here: http://v4.ident.me/
- The country you're from
- Your Aternos username
- Software and version installed on your server
- Does the problem also occur if you install the Vanilla server software on your server?
Please note that we can only take action if you comply with the above points and send us all the relevant information.