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I have a .net core app which spins up a grpc server. I was able to run it locally without a problem until I had Windows updates today. After Windows applied latest updates, I tried to run my .net core app, but I keep getting the following error.

System.IO.IOException: Failed to bind port "127.0.0.1:50001" at Grpc.Core.Server.CheckPortsBoundSuccessfully()

I went to firewall and opened access to the port that grpc has problem accessing. It did not help. Anybody had this issue?

neo
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  • which port is it trying to bind to? is something else using it? – Daniel A. White Jan 03 '19 at 16:13
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    I checked it is not being used. It is 50000 range – neo Jan 03 '19 at 16:14
  • This really looks like someone's using that port. Have you tried a different port? There isn't much complexity in binding the code that binds the port on the server side - it mostly just invokes the syscall to bind the port (and that seems to be failing). Can other servers (non-grpc) bind that port without a problem? – Jan Tattermusch Jan 10 '19 at 14:29
  • @neo Did you find a resolution to this? I'm having the exact same issue now on code that's been working fine for over a year. Port is NOT in use. – user3953989 Feb 06 '19 at 03:37
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    @user3953989 I posted the answer. – neo Feb 06 '19 at 20:48
  • @neo Thanks for the follow up and link! I came to this same conclusion but couldn't find any documentation to prove it. – user3953989 Feb 07 '19 at 02:25

2 Answers2

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I wasted 2 days on this and finally got the answer. Windows update caused certain valid to use ports to be excluded and as a result I couldn't run any app that listens on those excluded ports.

Here is a link to Microsoft article. Windows update blocking previously valid ports

neo
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    Your answer reminded of the right search, but the link is dead. Consider changing it to something like https://stackoverflow.com/questions/54010365/how-to-see-what-is-reserving-ephemeral-port-ranges-on-windows – Mads Ravn Nov 16 '21 at 08:13
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You can change the startup project to current selection by right click on your solution. or you can set multiple starup project as shown in pictur. it solve my issue.. step1

step 2 step 2

click apply

Ssd Suraaz
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