Solved - An attempt was made to access a socket in a way forbidden

Date Published: 03 November 2020

Solved - An attempt was made to access a socket in a way forbidden

I'm assuming you're here because you are seeing this error and are wondering why:

Microsoft.AspNetCore.Server.Kestrel[0]
      Unable to start Kestrel.
      System.IO.IOException: Failed to bind to address http://localhost:51816.
       ---> System.AggregateException: One or more errors occurred. (An attempt was made to access a socket in a way forbidden by its access permissions.) (An attempt was made to access a socket in a way forbidden by its access permissions.)
       ---> System.Net.Sockets.SocketException (10013): An attempt was made to access a socket in a way forbidden by its access permissions.
         at System.Net.Sockets.Socket.UpdateStatusAfterSocketErrorAndThrowException(SocketError error, String callerName)
         at System.Net.Sockets.Socket.DoBind(EndPoint endPointSnapshot, SocketAddress socketAddress)
         at System.Net.Sockets.Socket.Bind(EndPoint localEP)
         at Microsoft.AspNetCore.Server.Kestrel.Transport.Sockets.SocketConnectionListener.<Bind>g__BindSocket|13_0(<>c__DisplayClass13_0& )
         at Microsoft.AspNetCore.Server.Kestrel.Transport.Sockets.SocketConnectionListener.Bind()
         at Microsoft.AspNetCore.Server.Kestrel.Transport.Sockets.SocketTransportFactory.BindAsync(EndPoint endpoint, CancellationToken cancellationToken)
         at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Infrastructure.TransportManager.BindAsync(EndPoint endPoint, ConnectionDelegate connectionDelegate, EndpointConfig endpointConfig)
         at Microsoft.AspNetCore.Server.Kestrel.Core.KestrelServerImpl.<>c__DisplayClass29_0`1.<<StartAsync>g__OnBind|0>d.MoveNext()
      --- End of stack trace from previous location ---
         at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.AddressBinder.BindEndpointAsync(ListenOptions endpoint, AddressBindContext context)
         at Microsoft.AspNetCore.Server.Kestrel.Core.LocalhostListenOptions.BindAsync(AddressBindContext context)
         --- End of inner exception stack trace ---
       ---> (Inner Exception #1) System.Net.Sockets.SocketException (10013): An attempt was made to access a socket in a way forbidden by its access permissions.
         at System.Net.Sockets.Socket.UpdateStatusAfterSocketErrorAndThrowException(SocketError error, String callerName)
         at System.Net.Sockets.Socket.DoBind(EndPoint endPointSnapshot, SocketAddress socketAddress)
         at System.Net.Sockets.Socket.Bind(EndPoint localEP)
         at Microsoft.AspNetCore.Server.Kestrel.Transport.Sockets.SocketConnectionListener.<Bind>g__BindSocket|13_0(<>c__DisplayClass13_0& )
         at Microsoft.AspNetCore.Server.Kestrel.Transport.Sockets.SocketConnectionListener.Bind()
         at Microsoft.AspNetCore.Server.Kestrel.Transport.Sockets.SocketTransportFactory.BindAsync(EndPoint endpoint, CancellationToken cancellationToken)
         at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Infrastructure.TransportManager.BindAsync(EndPoint endPoint, ConnectionDelegate connectionDelegate, EndpointConfig endpointConfig)
         at Microsoft.AspNetCore.Server.Kestrel.Core.KestrelServerImpl.<>c__DisplayClass29_0`1.<<StartAsync>g__OnBind|0>d.MoveNext()
      --- End of stack trace from previous location ---
         at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.AddressBinder.BindEndpointAsync(ListenOptions endpoint, AddressBindContext context)
         at Microsoft.AspNetCore.Server.Kestrel.Core.LocalhostListenOptions.BindAsync(AddressBindContext context)

The reason is most likely due to a Windows Update that restricted access to certain ports on Windows machines. The details are here.

You can view a list of which ports are excluded from your user by running this command:

netsh interface ipv4 show excludedportrange protocol=tcp

On my Windows 10 machine I get this output:

Protocol tcp Port Exclusion Ranges

Start Port    End Port
----------    --------
      5357        5357
     49800       49899
     49900       49999
     50000       50059     *
     50060       50159
     50160       50259
     50260       50359
     50683       50782
     50783       50882
     50883       50982
     50983       51082
     51083       51182
     51777       51876
     51877       51976

* - Administered port exclusions.

Specifically, I had an ASP.NET Core web app that previously worked fine with ports 51814 and 51815 but then suddenly wouldn't start. Looking at the list above you can see this is in the range of 51777-51876.

After changing my ports, everything works again.

Steve Smith

About Ardalis

Software Engineer

Steve is an experienced software architect and trainer, focusing currently on ASP.NET Core and Domain-Driven Design.


Ardalis

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