How does Aspire find free ports?

[paulomorgado]

I need to set TCP ports on one of the projects.

It's not running on Kestrel.

[paulomorgado]

I could try using Kestrel, but it won't be HTTP/HTTPS.

[davidfowl]

What's the real question? What are you trying to do?

[paulomorgado]

I have code that uses a TcpListener and I would like to assign port dynamically when launching from Asipre host.

Other resources connect to these listeners.

Looks very similar to launching a ASP.NET Core project without launch profile.

[davidfowl]

Should work just fine. What’s not working ? Can you show your setup and what the problem is?

[paulomorgado]

I don't get it. What should work?

Right now I have a static port configured.

What I'd like to do is have a dynamic port that Aspire can configure other resources with.

[davidfowl]

Use WithEndpoint and set the env parameter. That will allocate a dynamic port and pass you the value so that you can bind to it.

[paulomorgado]

That's amazing! Didn't know that.

But now I'm curious, how is it done?