6mo ago

Local server can't be seen on Android or iOS, but can on any Linux device

192.168.x.x:1500

So I have a small local server running a website. It's not public facing at all, has a static IP address on my WiFi LAN and can be accessed by any Linux machine. I can't see it on any iPhone or Android device though

I've looked up tutorials on line, ensured my firewalls allow local sharing on the WiFi, double checked I can even ping the server successfully with nmap on Android

Any tips?

::edit:: typo in post, not when searching for IP on LAN

31 comments

Are you sure you are typing the address in correctly on android/ios? 198.162.x.x isnt part of private IP space.

Have you tried different browsers? You should also enter the full URL sometimes they're a bit stupid nowadays. So http://192.168.x.x:1500/
Maybe the browsers bring their own VPN. Some process all traffic to make it more "mobile friendly". Or they have some other kind of proxy.

Also check to make sure the mobile browsers aren't set to HTTPS only, or at least have an exception for that ip. I've seen that before several times.
- I’d curl from a machine on the same WiFi network as the phones just to confirm that HTTP is working. That way you’re not dependent on browsers that can be more finicky for debugging.

Some possibilities:
WiFi has host isolation is enabled
The network you're connecting from is a guest wifi network
You configured a firewall rule to isolate WiFi from LAN
VLAN is enabled
- I was assuming your server and Linux device were plugged in via Ethernet and your mobile devices were using WiFi. Now it sounds like your Linux system may be using the same access point.
  It could be something as simple as your browser trying to send the address to a search engine instead of directly looking for the site.
  When you're trying to access it on mobile do you manually enter "http://" or "https://"? Those default to ports 80 and 443 respectively.
  If you're using nonstandard ports you may need something like "http://192.168.1.42:8080" to use http on port 8080 or any other nonstandard port.
  Even if you are 100% sure your server is http or https try the other one to see if your error changes.

Are your phones on the same network? Same vlan? Firewall rules? VPN?
Does tcpdump on the server see the request?
- I get a lot of downvotes. I realize I say things that can be divisive. Why are people downvoting debugging steps? What's divisive about that....
  
  Don't worry about downvotes.
- Yeah, if phones go via WiFi and the computer is on a cable the IP ranges may differ and that would explain you can access only via one of the two.

I had some similar symptoms on a Fritzbox router, because by default the devices connected over wifi were unable to communicate with those connected by cable. Some routers also had this setting for the different wifi bands, 2.4G & 5G.
But I don't think you'd be able to ping it if this were the case.
Check yoyr router settings anyway, maybe you'll find something there.

My guess is that you are making a typo. Like others have said 192.162.x.x is a public IP. You probably want something like 192.168.x.x which probably is more like 192.168.1.1/24 with the last 1 being its own number

Your network is probably configured with inconsistent subnets / netmasks. iOS / Android are on WiFi and getting a different subnet/netmask than your severs.
Edit: What does pinging the server with nmap mean? Are you checking open ports or pinging the server? That doesn’t make sense or at least leaves us with more questions with the way you worded that. Although the nmap utility can provide both of those answers, I’m not sure that’s what you meant. Technically nmap and ping are two different tools.
- Same netmask?
  When asking for network troubleshooting assistance, super useful to provide ANY kind of network info. So far we have WiFi and same subnet. Yet absolutely no details which are necessary to help form questions or provide answer.
  Can you post the IP Netmask and Gateway of your Linux server and one of your mobile devices that can’t view the server?
  Can you ssh into the Linux server from your mobile device?

What error you get exactly?
- Install some DNS test app for Android and check that it does get resolved.
  My will resolve the home server address to 0.0.0.0, and I get the same network error.

Disable your mobile network and try again. I had the very similar issue where it would always fallback to the mobile network for local IPs although WiFi was connected and in the same subnet

network interface - check
dns - not applicable
firewall - check
ping - check
navigating to the web site - fail
There are two causes here. Either server fucks it self over or the client fucks itself over. For server check logs, for client: check spelling, specify full protocol and try different browser to pinpoint the problem. It would be great to see the full ip address output from 'ip -c a' on both client and server.
- PingTools has been useful for me (though I mostly just use it for iperf).

Any chance you have a DMZ set up on your router?
On your router, are there any settings specific to any host (other than the server maybe)? For example, a static IP or a port forwarded rule.
Do you have a VPN on the phones? Can you traceroute from your phone to the server and post that? (I like PingTools for Android.) You should have 1 hop (you -> server, nothing in between).
Can you verify that you are on the same wifi including same wifi channel? Phone on 5GHz but Linux box on 2.4GHz, for example.

Dunnon about iOS but some Android phones have a "network protection" config which uses a Google VPN, so it tends to block viewing the local network.
- It's listed as a privacy option on my pixel. It may be different for others but you could try searching the settings for "vpn" or "privacy."

I have a very similar issue. Seems like Android will bypass your DNS resolver and thus cannot resolve your local names.
I have my home services on "home.my domain.com" accessible from outside and re-mapped to "192.168.0.1" (my internal server IP) at home, and all PCs can access it while all android phones can only resolve to the public IP.
I feel it's something related to DoT or similar but haven't yet dig in that.

Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread:

Fewer Letters	More Letters
DNS	Domain Name Service/System
HTTP	Hypertext Transfer Protocol, the Web
HTTPS	HTTP over SSL
IP	Internet Protocol
SSL	Secure Sockets Layer, for transparent encryption
VPN	Virtual Private Network

5 acronyms in this thread; the most compressed thread commented on today has 13 acronyms.

[Thread #928 for this sub, first seen 20th Aug 2024, 15:45] [FAQ] [Full list] [Contact] [Source code]

might be your smartphone browser/system is using some kind of proxy. this could explain that you are able to ping, but the browser shows access denied. if no log entries are generated on the server when trying to access it via browser, it has to be something on client side or inbetween. on grapheneOS check: Settings - Network and Internet - Internet - Wifi-Settings - choose edit at top right - then advanced. If proxy is not set to none, change it and test again.
If this still doesn't help, my last bet is some kind of duplicate IP

Did you ever figure this out???

31 comments