Can find PMS remotely but not internally

Plex Media Server Desktops & Laptops
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Server Version#: 1.18.6.2368
Player Version#: 3.2.20-259990c775

I’m having regular trouble connecting to my Windows Server hosted PMS from the player application on two old Windows tablets (both running latest x86 version of Windows 10) and a Samsung TV. Regular and persistent problems:

  1. Cannot find PMS
  2. Can find PMS but cannot make a direct connection

Changing to Google’s DNS servers rather than my own DNS server seems to help find the PMS but not reliably. I haven’t identified exactly when connections will/won’t work correctly so I’m just listing details which may make sense to someone who knows more about the discovery process.
I can always connect to my PMS remotely from outside my home network.
When trying to connect locally at home:

  1. I can always browse to the IP address of the PMS an make an insecure connection using the computer which can’t find the PMS using the player app.
  2. It doesn’t make a difference if I use a wired or wireless connection
  3. I haven’t seen any problems with newer computers or laptops. They connect to the PMS and show a direct secure connection using the player app.
  4. A new PC which works just fine with the player app still shows an indirect connection when connecting to the PMS on the same network, via https://app.plex.tv/

Can anyone suggest any troubleshooting I could carry out to help me work out why these devices can’t find the PMS when they’re on the same network as it is?

Thanks

Robin

2

The Windows UWP app is deprecated and no longer available in the app store.

The Samsung app you are using is the old Orca app.
I’m afraid it won’t get any updates either.

If you can do without user authentication in your home network, you could disable the need for the tv, by putting its local IP address into
Settungs - Server - Network - ‘Show Advanced’ - “List of IP addresses and networks that are allowed without auth”

And you need to make sure that your router doesn’t interfere with Plex’s way of doing secure connections in the local network: https://support.plex.tv/articles/206225077-how-to-use-secure-server-connections#toc-4
(If you are using FIOS, disable its “Fios network protection”)

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I appreciate the response but it doesn’t help me much or seem to relate to my symptoms. I know the tv and tablets are more than 3 years old but I’m still hoping someone can help me get them to work more reliably.

There’s no other app available for either the x86 tablets or the TV and it seems unlikely this is compatibility related or I’d expect consistent failure.
The TV doesn’t have a problem with authentication, just occasional failing to find the PMS after successful authentication has competed.
Is there anything in that article which you think relates to this problem? I I read it before posting in this forum but the only likely point I got from it was that my ISP’s DNS could be the problem, that’s why I switched first to an internal DNS server then to Goggle’s public DNS servers.

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No, the main point of the article is that a (protective) feature in routers can cause your clients to either

  • prefer the indirect (but ‘secure’) route over the direct (but unsecure) route
  • not finding the server at all

It then goes on to tell possible names of this feature and how to modify it so it doesn’t interfere with Plex.

5

No it doesn’t. That article only lists DNS protective features from either the router or the ISP. I’ve confirmed I’m not using either the router or ISP’s DNS so can’t see the relevance.
I don’t want to fill a thread with arguments about this article and I don’t know how to fix the problem I’m experiencing.
If you or anyone else have any suggestions, please shout out.

6

That is weird. So how do you resolve domain names to IP adresses in your LAN?
Do you have a separate DNS resolver? If you do, chances are that this one implements ‘DNS rebinding protection’ itself. (And therefore needs to be instructed accordingly, to not do it anymore for the domain plex.direct.)

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I started with my ISP’s router as the DNS server. After reading that article I tried an internal hosted DNS server running on Windows server, that server was configured to use root hints for resolution, I also tried configuring it to forward all requests to Google’s public servers (8.8.8.8 and 8.8.4.4).
I’m currently setting all clients to directly use Google’s public servers. That seems more reliable but is still hit and miss and without keeping notes for a month or more I’m not absolutely certain its made a difference. The problems certainly still occur.

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I was told that some routers could intercept DNS queries made by devices in their local network.
I assume you disabled DNS in your router so it couldn’t do that?

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My router doesn’t have the option of disabling DNS but having a DNS server wouldn’t be related to reading and modifying the payload of UDP packets passing through a router.

10

In case it helps anyone, this seems to have been caused by IPv6 being disabled (not really disabled, just un-bound from the NIC) on the PMS at operating system level.
Disabling IPv6 support in Plex on the PMS to make all traffic IPv4 didn’t help.
Disabling IPv6 on clients got them working but re-enabling IPv6 on the server and clients has everything working correctly.

1 Like
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So in the beginning you had IPv6 unbound from the NIC, yet PMS did try to communicate with clients over IPv6?

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Yes, it was unbound from the NIC. I also disabled IPv6 in the PMS.
I can’t say for certain that clients tried to communicate over IPv6. I saw signs (which I didn’t follow thoroughly so this may be wrong) that name resolution was being attempted using IPv6 by the client. If that’s the case it could a failure to get an A/AAA record rather than subsequent communication. I don’t know enough about IPv6 to confirm what was happening.

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