Cast to Device (TV) fails: Unexpected Device Error

Just to be slightly silly, as the laptops are networked, I viewed an mp3 file on the PC that currently can't cast from the one that can - and cast that.

This problem is commonly reported - seems a bit like networking- fragile.

dalchina said:

Hi, I have two laptops, same build 19045.3693.

I can cast from one to my Panasonic TV, but not the other, both via Wi-fi.
The one that fails, fails as per the title.

Hi dalchina.

As you may recall, I also have a Panasonic TV, and I also regularly cast to it over DLNA from any of my PCs, both Windows 10 and 11. All are WiFi connected.

I have very occasionally seen the 'unexpected device error' in Cast to, but it's not specific to any one PC, and trying a second time usually works. At most I may need to turn the TV off and back on again.

Thanks. Unfortunately despite all efforts, 1 PC is 100% failing as shown.
Various days- and of course, PC and TV have been turned on and off repeatedly

By contrast it's 100% functional from the other PC. Both to the same router etc.

There must be one thing somewhere that needs changing on the PC that fails- but I can't find it.

I have now found a solution. This proved remarkably specific and technical.
None of the many guides to resolving this quite common problem helped.

First I turned to the event viewer where I found for each occurrence of the failure to cast

Unable to bind to the underlying transport for [::]:10246. The IP Listen-Only list may contain a reference to an interface which may not exist on this machine. The data field contains the error number.

Event id 15005

This looks daunting at first, but is in fact quite specific. It says port 10246 is not accessible.

netsh interface ipv4 show excludedportrange protocol=tcp

revealed a surprisingly large range of ports designated as administered port exclusions, including that one.

Further investigation showed that large numbers of ports may be blocked by
a. Hypervisor
b. Suspected malware
c. After some updates

Although I've not used Hypervisor, I had a vague memory of once enabling it to give it a whirl, and since the command to disable Hypervisor was said to be likely to remove this restriction on many ports, on something of a random whim I ran

Disable-WindowsOptionalFeature -Online -FeatureName Microsoft-Hyper-V-All
from an admin Powershell prompt.

The result was like configuring a Windows update, rather surprisingly.

I then tried casting an mp3 again.
It worked.

References:
IIS - The Process Cannot Access the File Because it is Being Used by Another Process

hyper v - What is Administered port exclusions in windows 10? - Stack Overflow

dalchina said:

I have now found a solution. This proved remarkably specific and technical.

That's very specific. No wonder you got little help from the forum!

Congratulations on your detective work.

Thanks.. and thanks to the event viewer reporting something I could meaningfully follow up. Also some useful internet pages.

The issue of port blocking would seem one that could have wider significance...

Now I still have one user-specific service that's not running on the other PC - but should be according to the registry keys and values... but with no apparent adverse effects. I thought it's absence might be causing this problem but it doesn't - if I stop it on my PC where Cast works, no adverse effect. From:
Restore Default Services in Windows 10 post #93


Update: having solved the port issue, the missing service now runs. So resolving the blocked port issue has resolved two problems.