This project demonstrates how to run Kestrel without ASP.NET. It creates a web endpoint on http://localhost:8080 which responds to all requests with "hello world".
It also demonstrates how to add the websocket middleware. If you connect to ws://localhost:8080 (with wscat, for example) it will again respond with "hello world". This time it will be sent as a textual websocket message.
Memory consumption is slightly better than ASP.NET, and startup time is a bit lower too, about 180ms on my system. On a Linux system, you can measure the startup time like this:
dotnet publish -c Release
time ./time-startup
On .NET 7, the techniques used here were the only way to use Kestrel with native AOT compilation. With .NET 8, the minimal APIs are supported with native AOT. For most projects, this will be a better option. If you still want to use Kestrel directly, this project may be useful.
As with .NET 7, you can build an AOT version if that is useful:
dotnet publish -r linux-x64 -c Release
(This has only been tested on Linux. If you are not on Linux, you could try building an executable, but you will need to substitute a different runtime identifier in the above command.)
Unfortunately, with .NET 8, UseHttps has a dependency on the KestrelMetrics class, which is internal. Instances of this class are created by reflection, and there is a TrimmerRootDescriptor in the .csproj file to ensure that all the necessary code is included in the final executable. This is unsatisfactory because it depends on the internal design of Kestrel. Also, the dotnet publish step displays trim warnings for this class even though they are supposed to be turned off; presumably this is a bug in the .NET SDK. If you have a better solution for any of this, please let me know!
The server now supports TLS. If you store a PKCS12 certificate in localhost.pfx, the server will listen for https connections on port 8080, rather than plain http.
For testing purposes (and only testing purposes) you can create a suitable self-signed certificate like this:
openssl req -x509 -newkey rsa:2048 -sha256 -keyout localhost.key -out localhost.crt -subj '/CN=test.com' -nodes
openssl pkcs12 -export -name localhost -out localhost.pfx -inkey localhost.key -in localhost.crt -passout pass:
To test the server, you will now need these commands:
curl --insecure https://localhost:8080
wscat --no-check -c wss://desktop.chown.org.uk:8080/ws