RESOLVED - Can't connect to home server from Android phone (lemm.ee)

submitted 2 weeks ago* (last edited 2 weeks ago) by perishthethought@lemm.ee to c/android@lemmy.world

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Hi folks, a little troubleshooting help here, please.

I have a Samsung Galaxy S9 with Android 10 rn. I use Firefox as my main browser, but I've tried this on others (Internet from Samsung, DuckDuckGo browser) and get the same result.

When I am at home, connected to my personal wifi network I want to connect to my self-hosted server at 192.168.68.137. In all browsers, just starting this week, I get "Can't connect to the server" or "ERR_ADDRESS_UNREACHABLE". This just was working fine the other day, but something (???) has changed and it won't connect. When I am trying this, my phone's IP is 192.168.68.106 so def on the same lan. And, my phone can connect to 192.168.68.100 without error - it's just the .137 address it can't connect to. This isn't a DNS issue; I am trying to reach it only via the IP address.

The server is definitely up and other PCs can connect to it just fine on the same LAN / 192.168 segment. I've tried rebooting the phone, same result. I turned off my pihole ad blocker - same result.

The craziest thing (to me) is that if I disable wifi on my phone, (so now it's on the cellular network) then connect my Wireguard VPN back into my home network, then I can browse to my home server. That should work, of course, but so should it work for me to connect while on the home wifi network without the VPN.

If anyone has any ideas, I would be very grateful.

EDIT: I rebooted the server and voila! The phone is connecting again. No idea why, but sure, OK. Thanks anyway, folks.

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[-] hungover_pilot@lemmy.world 3 points 2 weeks ago

Can you ping the server from your phone successfully? You can use an app like this to check: https://play.google.com/store/apps/details?id=net.he.networktools

Making sure you have layer 3 connectivity first would be a good first step. If you don't, I would start by troubleshooting at layer 2. Run a packet capture on both your phone and server while trying to connect to determine where the disconnect is. Make sure ARP is resolving properly.

If layer 3 IS working, move up to layer 4 and make sure you are using the correct port, http vs https, etc

[-] perishthethought@lemm.ee 2 points 2 weeks ago

I installed the suggested he.net app. Sending its Ping from the phone (.106) returns no responses from the server (.137).

I've no idea about the rest of what you wrote, or how to test layer 2 or 3 specifically. I've no way to run a packet capture, that I know of. Thanks for trying in any case.

[-] codapine@lemm.ee 1 points 2 weeks ago

You could try changing your host server's IP address and see if it still has the same issue (maybe it's added to a hosts file, or perhaps you installed no root firewall?) Can you ping 192.168.68.106 from your server? Not sure if ICMP echo traffic would be blocked by Android however.

Do both your server and phone have the same gateway/subnet mask?

[-] perishthethought@lemm.ee 1 points 2 weeks ago

Hey, thanks. I'd really rather not change the server's IP; it runs a number of docker-based services and I have other PCs configured to use the current address (like Rokus).

Can a stock Android phone have a custom HOSTS file? Or could there be a firewall I didn't install?

I tried pinging the phone from the server. No responses at all. Not sure if that's normal for Android or not.

Both the server and phone have static IPs assigned and use the same gateway - 192.168.68.1 / 24.

[-] codapine@lemm.ee 2 points 2 weeks ago* (last edited 2 weeks ago)

Stock android without an unlocked bootloader will not give you access to the hosts file, and there shouldn't be a firewall you don't know about. Can you run a vbox or live USB on another machine on your network to see if it will see the server?

I just saw you already answered about the same gateway and mask. Hm. I'm thinking there's probably a janky setting on your router, that's the only place I can think of that might have a poorly configured or unconfiugred firewall. Especially if it works on the cellular using the VPN.

Good luck with it, I'm sorry I don't have the exact answer!

Edit - just saw your edit. Computing is like that sometimes! Glad you got it working. 👍

[-] perishthethought@lemm.ee 1 points 2 weeks ago

Thanks again and yep, I should have thought to reboot the server sooner.

I had a thought after all the above. What if there were two devices in the lan with that same .137 IP? It's inside the DHCP range but I thought having the router reserve the 137 address for my server would mean no other PC could get it.

I'm gonna check out that angle, move the server to an IP outside the DHCP range next.

this post was submitted on 17 May 2024

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