How to make service discovery work between two projects with non HTTP traffic

[pfeigl]

I've a very basic setup:

• Aspire AppHost
• Server project based on MQTTnet hosting a mqtt server
• Client (server-based) blazor application trying to connect to the mqtt server

This is pretty much my code in the blazor app to try connect to the mqtt server

var mqttClientOptions = new MqttClientOptionsBuilder()
    .WithTcpServer("mqtt-server", 1883)
    .Build();

await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);

And this is pretty much my AppHost setup

var mqttServer = builder.AddProject<RobotRemoteControl_Server>("mqtt-server")
    .WithEndpoint(targetPort: 1883, scheme: "tcp", env: "MQTT_SERVER_PORT");

builder.AddProject<RobotRemoteControl_UI>("robotremotecontrol-ui")
    .WithReference(mqttServer);

From the dashboard, all endpoints seem to be correct.
I checked the code of the MQTTnet client library and internally it seems to simply open a socket connection based on an DnsEndPoint.

No matter what I tried, it won't resolve the mqtt-server host.
I'm probably missing something or the whole point.

Thanks for any help