Error Dlna: Error in BeginListeningForBroadcasts

[softworkz 4574]

Having the same problem here. EmbyServer tries to open UDP port 1900 for SSDP exclusively, which is a bad idea.

• When I start EmbyServer first, it works fine, but several other applications then fail to open port 1900.
• If one of the other applications is started first, other applications can share port 1900 fine, but I get the described error from EmbyServer.

SSDP is often used by multiple processes for service discovery like DLNA and (at least on Linux) should be opened with the SO_REUSEADDR socket option set.

 

EmbyServer sets SO_REUSEPORT (twice), but not SO_REUSEADDR. Some quick tests with Python show that Linux requires SO_REUSEADDR to be set for sharing multicast UDP ports, SO_REUSEPORT does not work.

 

 

@@f69m - your findings are correct in every detail except one: It's the .net core Linux runtime that is doing wrong, while Emby is correctly requesting SO_REUSEADDR.

 

 

We've not only narrowed down the cause, we know precisely why it happens down to the Unix native .net core runtime implementation . This is from an internal mail on this subject:

 

The problem was introduced with .net core 2.1. It had worked fine with previous versions:

 

Reported here for example: https://github.com/dotnet/corefx/issues/32027

 

This is the commit that screwed things for .net core 2.1: https://github.com/dotnet/corefx/commit/7eba4bf88983ac276348ea1626c81595e1b237c6#diff-3c0edd8d16aa366989215dba11a0bc08

 

Unfortunately it has not yet been resolved in .net core 2.2:

 

https://github.com/dotnet/corefx/blob/release/2.2/src/Native/Unix/System.Native/pal_networking.c

 

 

This is the PR that has been merged and will fix the behavior for .net core 3.0:

 

https://github.com/dotnet/corefx/pull/32046/files

 

 

Conclusion

Until .net core 3.0, there's nothing we can do, I think.

(except some crazy stuff maybe, but that would need quite a bit time to work on)

Edited December 31, 2018 by softworkz

[Luke 40125]

.NET Core 3.0 is scheduled for release in March.

[softworkz 4574]

I think, this is something we can (and should) wait for.

 

Before someone might ask what I meant by 'crazy things' - that would have been either:

• Backport the fix to .net core 2.2, then compile and distribute a custom version of the .net core 2.2 runtime for Linux
  ...or...
• Try to p/invoke some native calls to set the required socket option

Both variants are easily written down but horrible to accomplish.

 

So let it be those 2-3 months....

[f69m 0]

Thanks for the quick response and for all the details. Yeah, the breaking change was for TCP, where using SO_REUSEPORT makes sense, but it is different for UDP. Oh well, lets wait for 3.0...

[joho500 1]

I am using BubbleUpnpServer on Linux and found out that making a proxy for Emby Server is working to make Emby Server available as dlna server despite it currently not working on its own.

 

FYI

 

Cheers,

Joost

[Luke 40125]

Thanks for the info.

[Luke 40125]

This exception should be resolved in the Emby Server 4.2 beta builds if you guys would like to try that. Thanks.