Building bidirectional Streaming gRPC : A Real-World chat Example

A real-world example of bidirectional streaming using gRPC in a Spring Boot application with a REST wrapper for client interaction.

🔧 Technologies Used

• Java 11
• Spring Boot 2.7.x
• gRPC (1.54.0)
• Protocol Buffers (proto3)
• Maven
• WebFlux + Server-Sent Events (SSE) for REST integration

✅Code Repository Link 

Link - grpc-bidirectional-chat-server-client

1. Start gRPC Server

• cd grpc-bidirectional-chat
  mvn clean install
  mvn spring-boot:run

2. Start REST Clien

• cd grpc-bidirectional-chat-client
  mvn clean install
  mvn spring-boot:run

3. Upload a File via REST

• curl -X POST "http://localhost:8081/chat?sender=Alice&message=Hello"

✅ Project Structure

Server: grpc-bidirectional-chat

---

• grpc-bidirectional-chat/
  ├── pom.xml
  ├── src
  │   ├── main
  │   │   ├── java/com/example/grpc/
  │   │   │   ├── ChatServiceImpl.java             # gRPC service impl
  │   │   │   └── GrpcServerApplication.java   # Spring Boot entry
  │   │   └── resources/
  │   │       └── application.yml
  │   └── proto/
  │       └── chat.proto                                        # gRPC contract

Client: grpc-bidirectional-chat-client

---

• grpc-bidirectional-chat-client/
  ├── pom.xml
  ├── src
  │   ├── main
  │   │   ├── java/com/example/grpc/
  │   │   │   ├── ChatController.java                # REST controller
  │   │   │   └── GrpcClientApplication.java    # Spring Boot entry
  │   │   └── resources/
  │   │       └── application.yml

🧠 Class Responsibilities

---

🟢 Server

• GrpcServerApplication.java
  → Main Spring Boot entry point for the gRPC server.

• ChatServiceImpl.java
  → Implements the gRPC ChatService and handles bidirectional chat streams.

🔵 Client

• GrpcClientApplication.java
  → Main Spring Boot entry for the client REST API wrapper.

• ChatController.java
  → Exposes a /chat REST endpoint to initiate gRPC bidirectional streaming using stub.

🧬 Proto File 

---

• syntax = "proto3";
  
  option java_multiple_files = true;
  option java_package = "com.example.grpc";
  option java_outer_classname = "ChatProto";
  
  service ChatService {
    rpc chatStream (stream ChatMessage) returns (stream ChatMessage);
  }
  
  message ChatMessage {
    string sender = 1;
    string message = 2;
    int64 timestamp = 3;
  }

🔁 Diagram: REST → gRPC Flowe

---

• [POST /chat?sender=Alice&message=Hello]
           |
           v
  +-------------------+
  | Spring Controller |
  +-------------------+
           |
           v
  +------------------------+
  | gRPC Async Stub (Client) |
  +------------------------+
           |
           v
  +------------------------+
  | gRPC Server Impl       |
  | - ChatServiceImpl      |
  +------------------------+
           |
           v
  [Responds back via StreamObserver]

When to Use gRPC bidirectional Streaming

✅ Anti-Patterns / When Not to Use It

⚖️ gRPC Bidirectional vs Other Streaming Protocols

🚀 ALL Spring boot gRPc Post 

Spring Boot gRPc All Post