I am having the same issue. I have had my server running for a long time, with no issues. 2 days ago, my friends and I were all playing on the server, ( which I have hosted from my personal PC ), and they all suddenly disconnected. They texted me telling me my server was down, (while I am still locally playing on the server). I tried to connect through my external address, and it will not let me connect. I have been battling this problem ever since...
Found a solution. I connected my pc straight to my modem ( bypassing my router ) and pulled my external ip address. It was different than the one I was getting when going through my router.
I connected externally to my world with my router bypassed. ( adding the new ip address into my multiplayer server list )
I shut everything down, hooked my router back up, and when I pulled my external ip address again, it gave my the one it origionally did.
When I fired up Minecraft, and looked for my server externally, it showed the one listed under the ip address given by directly connecting my computer to my modem. ( I can not explain why when I connect my router to my modem, and pull my ip address that way, that I receive a false IP ) But I can say that finding out what IP address you get while connected directly to your modem and then using that address while connected to your router should solve the issue ( at least it did in my case )
Hope this helps.
Edit - No longer working ... Not sure whats happening.
Bumping is against the forum rules. And your problem is this:
If you're using the SAME computer as the server is running on use the IP: localhost
If you're using a computer on the same NETWORK (LAN) then use its (internal) IP address
If you're using a different computer OUTSIDE of your LAN use it's external IP address
Bottom line: Instead or using your external IP address you should be using "localhost" (Without quotes) for your IP. Hope that helped.
P.S. You must either use LogMeIn Hamachi OR Port forward for people outside your home network to join. They will use the external IP.
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