We have written (in Go and Delphi) several Windows microservices, which respond to HTTP requests on specific ports in the 11000-12000 range. These are designed to run internally within the Domain or Private network of the client (i.e. not on the internet).
They run perfectly on all but one of our 50+ client systems, on OS's ranging from Windows 7/10/11 to Windows Server 2008R2/2012/2016/2019. The installation process for each of these services sets up rules in the Windows firewall to accept the requests to each service exe.
The one client system that they dont work on is running Windows Server 2016 Essentials. This is the only client system running that specific OS, so that may be a factor in the problem.
Even locally using a web browser on that system to query the services they dont work. The requests just wait for a while and then timeout: ERR_CONNECTION_TIMED_OUT.
However the same requests to the same ports at address 127.0.0.1 (localhost) work instantly - proving the services are actually running.
The mode of failure when the targeted service is not running, or if we address the wrong port, is different. In that case we get a quick "refused to connect" failure: ERR_CONNECTION_REFUSED
There are no third party antivirus or firewall products installed on the system, which is only using Windows Defender with the normal Windows firewall. We've tried everything we can think of with the Windows firewall, including turning it off completely. Nothing we've tried made any difference.
We've tried using many alternative port numbers, but we dont get any success until we get up to the 49000 range and above, but we'd really rather not have to change from our normal port number range unless its completely unavoidable.
We've spent many hours trying to find any solution without any luck. We are really hoping that some bright person out there has some idea that will lead to finding the cause of the problem.
