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gRPC & High Performance APIs · Lección

Streaming bidireccional

Domine el streaming bidireccional, que permite al cliente y al servidor enviar simultáneamente una secuencia de mensajes.

Streaming bidireccional es una lección gratuita de gRPC & High Performance APIs en CoddyKit. Esta es la lección 3 de 4. Puedes leer la lección completa abajo gratuitamente — luego la practicas en el navegador con un editor de código integrado y un tutor de IA 24/7. Forma parte de la ruta de aprendizaje de gRPC & High Performance APIs, y tu progreso se sincroniza en la web y la app de CoddyKit. El curso de gRPC & High Performance APIs incluye 4 lecciones en total.

Partes de esta lección aún no han sido traducidas y se muestran en inglés.

Bidirectional Streaming: Two-Way Talk

What if both sides in a conversation could speak and listen at the same time? That's bidirectional streaming in gRPC! It allows both the client and server to send a sequence of messages to each other, concurrently.

Why Use Bidi Streaming?

Bidirectional streaming is perfect for applications needing real-time, interactive communication. Think of it like a phone call where both parties can talk and hear simultaneously.

  • Chat applications: Users send and receive messages instantly.
  • Live updates: Servers push data to clients as events happen.
  • Gaming: Synchronized game state updates between players and server.

Defining a Bidi Stream Service

To enable bidirectional streaming, you use the stream keyword for both the request and response types in your .proto file.

This tells gRPC that the method will handle a continuous flow of messages in both directions.

syntax = "proto3";

package chat;

message ChatMessage {
  string user = 1;
  string message = 2;
}

service ChatService {
  rpc Chat(stream ChatMessage) returns (stream ChatMessage);
}

Server: Receiving Client Messages

On the server, your service method will receive a StreamObserver for the incoming client messages. You'll implement its methods to process each message.

  • onNext(msg): Called for each message from the client.
  • onError(t): Called if the client stream encounters an error.
  • onCompleted(): Called when the client finishes sending messages.

Server: Sending Back Responses

The server also gets a StreamObserver (usually named responseObserver) to send messages back to the client. This allows the server to push multiple responses.

  • responseObserver.onNext(resp): Sends a message to the client.
  • responseObserver.onError(t): Signals an error to the client.
  • responseObserver.onCompleted(): Closes the server's outgoing stream.

Client: Starting the Conversation

On the client, you'll use an asynchronous (non-blocking) stub to call the streaming method. This call immediately returns a StreamObserver.

This returned observer is what the client uses to send messages to the server.

Client: Two-Way Communication

The client needs two main parts for bidirectional streaming:

  1. An observer for outgoing messages: This is used to onNext() messages to the server.
  2. An observer for incoming messages: This is passed to the gRPC call to handle responses from the server.

Both streams operate independently and concurrently.

Full Server Bidi Stream Example

Here's a simplified gRPC server that echoes messages received from the client. Remember to compile your .proto file and include gRPC dependencies.

Try running this example:

import io.grpc.Server;
import io.grpc.ServerBuilder;
import io.grpc.stub.StreamObserver;

// Assuming ChatServiceGrpc and ChatMessage are generated
// from the proto definition.
import chat.ChatServiceGrpc;
import chat.ChatMessage;

public class ChatServer {

  public static void main(String[] args) throws Exception {
    Server server = ServerBuilder.forPort(50051)
        .addService(new ChatServiceImpl())
        .build();

    server.start();
    System.out.println("Server started on port 50051");
    server.awaitTermination();
  }

  static class ChatServiceImpl extends ChatServiceGrpc.ChatServiceImplBase {
    @Override
    public StreamObserver<ChatMessage> chat(
        final StreamObserver<ChatMessage> responseObserver) {

      return new StreamObserver<ChatMessage>() {
        @Override
        public void onNext(ChatMessage request) {
          // Received a message from the client
          System.out.println("Server received: " + request.getMessage());
          // Echo it back to the client
          ChatMessage response = ChatMessage.newBuilder()
              .setUser("Server")
              .setMessage("Echo: " + request.getMessage())
              .build();
          responseObserver.onNext(response);
        }

        @Override
        public void onError(Throwable t) {
          System.err.println("Server error: " + t.getMessage());
        }

        @Override
        public void onCompleted() {
          System.out.println("Client stream completed.");
          responseObserver.onCompleted(); // Close server stream
        }
      };
    }
  }
}

Full Client Bidi Stream Example

This client sends a few messages and listens for responses. Run the server first, then this client. The client will send messages and print the server's echoes.

Try running this example:

import io.grpc.ManagedChannel;
import io.grpc.ManagedChannelBuilder;
import io.grpc.stub.StreamObserver;

// Assuming ChatServiceGrpc and ChatMessage are generated
// from the proto definition.
import chat.ChatServiceGrpc;
import chat.ChatMessage;

import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;

public class ChatClient {

  public static void main(String[] args) throws Exception {
    ManagedChannel channel = ManagedChannelBuilder.forAddress("localhost", 50051)
        .usePlaintext() // For demonstration, use TLS in production
        .build();

    ChatServiceGrpc.ChatStub asyncStub = ChatServiceGrpc.newStub(channel);

    CountDownLatch finishLatch = new CountDownLatch(1);

    StreamObserver<ChatMessage> requestObserver = asyncStub.chat(
        new StreamObserver<ChatMessage>() {
          @Override
          public void onNext(ChatMessage response) {
            System.out.println("Client received: " + response.getMessage());
          }

          @Override
          public void onError(Throwable t) {
            System.err.println("Client error: " + t.getMessage());
            finishLatch.countDown();
          }

          @Override
          public void onCompleted() {
            System.out.println("Server stream completed.");
            finishLatch.countDown();
          }
        });

    try {
      // Client sends messages
      for (int i = 0; i < 3; i++) {
        ChatMessage request = ChatMessage.newBuilder()
            .setUser("Client")
            .setMessage("Hello " + i)
            .build();
        requestObserver.onNext(request);
        Thread.sleep(500); // Simulate delay
      }
    } catch (RuntimeException | InterruptedException e) {
      requestObserver.onError(e);
      throw e;
    } finally {
      requestObserver.onCompleted(); // Client finishes sending
    }

    if (!finishLatch.await(1, TimeUnit.MINUTES)) {
      System.err.println("Client timed out waiting for server response.");
    }
    channel.shutdownNow().awaitTermination(5, TimeUnit.SECONDS);
  }
}

Bidirectional Stream Check

You've learned about bidirectional streaming. Which statement best describes how both client and server communicate in a gRPC bidirectional stream?

Bidirectional Streaming Recap

Great job! You've mastered bidirectional streaming in gRPC.

  • It enables both client and server to send sequences of messages.
  • Ideal for real-time, interactive applications like chat.
  • Defined using the stream keyword for both request and response in Protobuf.
  • Requires separate logic on both client and server to manage incoming and outgoing message streams.

This powerful pattern opens up many possibilities for highly responsive distributed systems.

Preguntas frecuentes

¿La lección «Streaming bidireccional» es gratis?

Sí — el texto completo de «Streaming bidireccional» es gratis para leer aquí en la web. Para practicarla de forma interactiva (editor de código integrado y tutor de IA 24/7) y desbloquear el resto del curso de gRPC & High Performance APIs, actualiza a CoddyKit PRO. El curso de gRPC & High Performance APIs incluye 4 lecciones en total.

¿Qué aprenderé en «Streaming bidireccional»?

Domine el streaming bidireccional, que permite al cliente y al servidor enviar simultáneamente una secuencia de mensajes. Practicas gRPC & High Performance APIs con código real que ejecutas directamente en el navegador, y un tutor de IA 24/7 responde tus preguntas mientras trabajas en la lección.

¿Necesito experiencia previa para empezar gRPC & High Performance APIs?

No se requiere experiencia previa. gRPC & High Performance APIs en CoddyKit está estructurado para principiantes hasta estudiantes avanzados, así que puedes empezar aquí o desde el inicio y avanzar a tu ritmo. Esta es la lección 3 de 4.

¿Cuánto tiempo toma la lección «Streaming bidireccional»?

La mayoría de las lecciones de CoddyKit toman alrededor de 5–10 minutos. Cada una es compacta e interactiva, así que avanzas constantemente y retomas exactamente por donde dejaste en la web y la app.

¿Puedo escribir y ejecutar código en esta lección de gRPC & High Performance APIs?

Sí. Cada lección de gRPC & High Performance APIs incluye un editor de código integrado, así que escribes y ejecutas código real directamente en tu navegador y obtienes retroalimentación instantánea de IA — sin configuración local necesaria.

Todas las lecciones de este curso

  1. Explicación del streaming del servidor
  2. Explicación del streaming del cliente
  3. Streaming bidireccional
  4. Control de flujo y backpressure en streams
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