🧪 Lab repo for test/implement NestJS native microservice with TCP communication. I will use monorepo mode to put client and server in the same project.

• nest new project_name -> This create a standard HTTP aplication.
• cd project_name
• nest generate app app_name -> This converts the "normal" app workspace to a monorepo workspace. We can see a new directory called /apps, inside there we find the project_name HTTP app and the new app_name recently created.

• @nestjs/microservices dependency installed

Here we create a microservice using createMicroservice method of NestFactory

const microserviceOptions: MicroserviceOptions = {
transport: Transport.TCP,
options: {
host: '127.0.0.1',
port: 3001,
},
};
const app = await NestFactory.createMicroservice(MicroserviceTcpModule, microserviceOptions);
await app.listen();

We use @MessagePattern to indicate request-response paradigm. In the below code, the getRooster() listens for messages that fulfill the 'getRooster' message pattern.

  @MessagePattern('getRooster')
  getRooster(): string {
    return this.microserviceTcpService.getRooster();
  }

The only thing we need to set is the ClientProxy in the service . This proxy allow us to communicate the client with the microservice.

  private client: ClientProxy;

  constructor() {
    this.client = ClientProxyFactory.create({
      transport: Transport.TCP,
      options: {
        host: '127.0.0.1', // microservice host
        port: 3001, // microservice port
      }
    });
  }

Once the communication is established we can execute send method to make the request.

/*
 The second parameter is empty string because getRooster doesn't receive any parameter, 
 but is mandatory in send method indicate one.
 */
return this.client.send('getRooster', '');