How to enable external request in IIS Express and MQTTnet

Question

i was able to access normal iisexpress-webservices from extern with change of ....vs\DashboardCore\config\applicationhost.config

when adding more bindings with my hostname:

/<bindings>
  <binding protocol="http" bindingInformation="*:5001:127.0.0.1" />
            <binding protocol="http" bindingInformation="*:5001:localhost" />
            <binding protocol="http" bindingInformation="*:5000:localhost" />
            <binding protocol="http" bindingInformation="*:47200:localhost" />
            <binding protocol="https" bindingInformation="*:44334:localhost" />
            
            <binding protocol="http" bindingInformation="*:5001:nb080.mydomain.local" />
            <binding protocol="http" bindingInformation="*:5000:nb080.mydomain.local" />
            <binding protocol="http" bindingInformation="*:47200:nb080.mydomain.local" />
            <binding protocol="https" bindingInformation="*:44334:nb080.mydomain.local" />
</bindings>

but MQTTnet from the client still works only with

var url = "localhost:5001/mqtt";

and not with

var url = "nb080.mydomain.local:5001/mqtt";

            var options = new ManagedMqttClientOptionsBuilder()
                .WithAutoReconnectDelay(TimeSpan.FromSeconds(5))
                .WithClientOptions(new MqttClientOptionsBuilder()
                    .WithClientId($"Client {printer}")
                    .WithWebSocketServer(url)
                    .WithCredentials(database, hash)
                    .Build())
                .Build();

i expect that mqttnet also uses the hostname.

my launchsettings.json looks like

{
    "$schema": "http://json.schemastore.org/launchsettings.json",
    "iisSettings": {
        "windowsAuthentication": false,
        "anonymousAuthentication": true,
        "iisExpress": {
            "applicationUrl": "http://localhost:5001",
            "sslPort": 44334
        }
    },
    "profiles": {
        "IIS Express": {
            "commandName": "IISExpress",
            "launchBrowser": true,
            "launchUrl": "weatherforecast",
            "environmentVariables": {
                "ASPNETCORE_ENVIRONMENT": "Development"
            }
        }
    }
}