Question Game server port closes after specific local PC disconnects or server is restarted.

l4whitney

Commendable
Mar 30, 2020
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I am currently running a Minecraft server for a few friends on a laptop connected to a TELUS Wi-Fi Hub. I have successfully configured it so that both local and global users can connect and everything works fine EXCEPT that when my roommate disconnects from the server or the server is restarted on a local connection. Important details:
  • The user's PC is hardwired in to an ethernet switch which runs straight to the router. They are on port 4 of 5, this does not seem overly important to me.
  • This is exclusive to the user's PC. My PC is hardwired via the same pathway to the router and does not cause this issue
  • all local users are connecting via the server's local IPv4
  • It does not matter whether they are the last user on the server or there are multiple people still in the server on both local and global connections
  • all users currently in the server remain connected until they end the session. This issue only affects the port itself.
  • This only happens when the user is connect via a local connection. When connected via global IP address using my phone as a hotspot, disconnecting does not close the port
  • This still happens when the user is connected via wi-fi to an auxiliary router that is hardwired to the ethernet switch that runs to the main router.
  • setting a static IP for the PC did not fix the issue
  • Setting the PC's local IPv4 as a DMZ did not fix the issue
  • disabling intrusion detection on the router did not fix the issue
  • updating/installing java (JRE and JDK) did not fix the issue
  • I have double checked that all java related executables are allowed through the firewall, namely whatever was in the firewall already (2 instances of javaw.exe) and the freshly installed java.exe and javaw.exe from the freshly installed jdk and jre (possibly redundant idk)
  • Logging into the router, editing the port, and saving the settings without changing them seems to refresh the port and open it back up. The current fix is to just refresh the port whenever the user leaves the server or the server is restarted.
I have zero clue what the issue could be. The user doesn't even use the port to connect to the computer since it connects via LAN. I assume it's something to do with the router shutting down the port under specific conditions. Unfortunately this router does not seem particularly geared towards server hosting or advanced tools or resources. I'm not really worried about the server restart issue as re-forwarding the port every now and then isn't too bad, but having to re-forward the port EVERY TIME my roommate disconnects is excessive, and honestly its bothering me not knowing what the hell is going on. Stuff like this happens to me every time I try to anything remotely network related and at this point I'm convinced that I'm being haunted by some cyber ghost or demon.

If anyone has ever dealt with something like this or knows what's going on I would be super grateful for any input you can provide (the port issue, not the maleficent network spirits) .
 
What do you mean the game server port closes. I assume you mean on the server itself ?

So the key things here is you say they are using the local IPv4 address. This means the traffic is actually going between the devices and the server via mac address. This is how all lan traffic works. The lan ports on the router are acting as a simple switch. You need to think of it as a 5 port switch with 4 lan ports and the fifth going to the router chip. It is as if you bought a router with 1 port and used a external switch. The traffic will go directly between the ports and never enter the router chip and not be affected by anything that is configured on it.

Now if you had said they were access the server Via the external IP that is far different since then the data must pass the router cpu multiple times.

Not sure this almost has to be some strange server problem. You might see something interesting if you were to run a wireshark capture on either the client machine that is causing the problem or maybe the server.
 

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