Connecting to microservice (MQTT)

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[ ] Regression 
[X] Bug report
[ ] Feature request
[X] Documentation issue or request
[ ] Support request => Please do not submit support request here, instead post your question on Stack Overflow.

Current behavior

Endless connecting without exception or success to microservice.

Expected behavior

Exception or successful connection.

Minimal reproduction of the problem with instructions

main.ts

import { INestMicroservice } from "@nestjs/common";
import { NestFactory } from "@nestjs/core";
import { Transport } from "@nestjs/microservices";
import { AppModule } from "./app.module";

async function bootstrap(): Promise<void> {
  const app: INestMicroservice = await NestFactory.createMicroservice(
    AppModule,
    {
      transport: Transport.MQTT,
      options: {
        host: "broker.hivemq.com",
        port: 1883
      }
    }
  );
  await app.listenAsync();
}

bootstrap();

app.module.ts

import { Module } from "@nestjs/common";
import { AppService } from "./app.service";

@Module({
  providers: [AppService]
})
export class AppModule {}

app.service.ts

import { Injectable, Logger } from "@nestjs/common";
import { Client, ClientProxy, Transport } from "@nestjs/microservices";
import { Observable } from "rxjs";

@Injectable()
export class AppService {
  @Client({ transport: Transport.MQTT })
  public client: ClientProxy;

  public async onModuleInit(): Promise<void> {
    Logger.log("Connecting");
    await this.client.connect();
    Logger.log("Connected");
  }

  public sendMessage(): Observable<number> {
    const pattern: {} = { cmd: "sum" };
    const data: number[] = [5, 6];

    return this.client.send<number>(pattern, data);
  }
}

What is the motivation / use case for changing the behavior?

Environment

Nest version: 5.3.0

 
For Tooling issues:
- Node version: 10.9.0
- Platform:  Mac OS

Others:

You can use the broker.hivemq.com which is publicly accessible and actually works.

[kamilmysliwiec]

My current understanding is that the Nest microservice connection will be used for listening on all message patterns in my controllers. The ClientProxy again can be a completely different transport which I could (additionally) send messages to. Is that correct?

Exactly.

it will always connect to 127.0.0.1:1883. When I use hostname instead of host with the exact same values it does connect just fine. The MQTT library code however says:

As I mentioned, this interface is an external one, it comes directly from MQTT library https://github.com/mqttjs/MQTT.js/blob/master/types/lib/client-options.d.ts. We simply pass down all options properties to the MqttClient instance.

does this mean it is connected to the broker specified in the createMicroservice options?

Yes

[kamilmysliwiec]

MQTT transport works properly as well. Not sure it cannot connect only to broker.hivemq.com