gRPC Proof of Concept (POC)

This repository is a proof of concept (POC) demonstrating how to implement and test different gRPC communication patterns in .NET, including:

• ✅ Unary gRPC
• ✅ Server‑side streaming
• ✅ Bi‑directional streaming
• ✅ JSON Transcoding (gRPC ↔ REST)

The solution also includes a .NET Console–based gRPC client used to test streaming scenarios that are not easily testable via browsers or REST tools.

---

📂 Solution Structure

The solution contains two projects:

GrpcService.sln
│
├── GrpcService              # gRPC Server (.NET)
│   ├── Protos
│   │   └── v1
│   │       ├── auth.proto
│   │       ├── greet.proto
│   │       ├── stream.proto
│   │       └── bidirectional.proto
│   │
│   ├── Services
│   │   ├── AuthService.cs
│   │   ├── GreeterService.cs
│   │   ├── LocationService.cs
│   │   └── LocationTrackerService.cs
│   │
│   ├── appsettings.json
│   └── Program.cs
│
└── GrpcLocationClient       # gRPC Client (.NET Console App)
    ├── Clients
    │   ├── Interfaces
    │   │   └── IClient.cs
    │   ├── BidirectionalStreamClient.cs
    │   └── ServerStreamClient.cs
    │
    ├── Protos
    │   └── v1
    │       ├── stream.proto
    │       └── bidirectional.proto
    │
    └── Program.cs

---

🔌 gRPC Communication Patterns Covered

1️⃣ Unary gRPC

• Request–Response communication
• Implemented in AuthService
• Used for JWT authentication

Client → Request → Server
Client ← Response ← Server

JSON Transcoding (REST support)

Unary gRPC is exposed as a REST endpoint using JSON Transcoding.

import "google/api/annotations.proto";

service Authorizer {
  rpc JwtAuth (AuthRequest) returns (AuthResponse) {
    option (google.api.http) = {
      post: "/api/v1/auth",
      body: "*"
    };
  }
}

✅ Can be tested via:

• Postman (gRPC protocol)
• Web browser / REST client (HTTP)

---

2️⃣ Server‑Side Streaming

• Client sends one request
• Server sends multiple responses as a stream

Client → Request
Server → Stream(Response)

Used to demonstrate scenarios like:

• Continuous updates
• Notifications
• Data feeds

Tested via the Console gRPC Client.

---

3️⃣ Bi‑Directional Streaming

• Client and server send streams simultaneously
• Full‑duplex communication over a single HTTP/2 connection

Client ⇄ Server (Streams in both directions)

Example use case implemented:

• Client sends live user location (lat, long, id)
• Server streams back nearby bus locations

This pattern is ideal for:

• Real‑time tracking
• Live maps
• IoT & telemetry systems

Tested via a .NET Console gRPC Client.

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🧪 Testing Strategy

Unary gRPC

• ✅ Postman (gRPC)
• ✅ REST via JSON Transcoding
• ✅ Browser (HTTP endpoint)

Streaming gRPC

• ❌ Not supported via REST / browsers
• ✅ Tested using .NET Console Client

The client application contains separate implementations for:

• Server‑side streaming
• Bi‑directional streaming

---

🧠 Why Console Client?

Streaming gRPC requires:

• Persistent HTTP/2 connections
• Open streams for continuous data flow

These features are not supported by typical REST tools or browsers, so a native gRPC client is required for:

• Server‑side streaming
• Bi‑directional streaming

---

🧱 Technologies Used

• .NET (ASP.NET Core gRPC)
• gRPC
• Protocol Buffers (proto3)
• JSON Transcoding
• HTTP/2
• Swagger / OpenAPI (for transcoded HTTP APIs)
• Postman (for gRPC testing)

---

📌 Notes

• Protobuf files are versioned under Protos/v1
• JSON Transcoding is intentionally applied only to unary gRPC
• Streaming endpoints are pure gRPC by design
• Swagger UI is enabled only for transcoded unary gRPC endpoints

---

🔀 JSON Transcoding & Swagger Support

This project integrates JSON Transcoding to expose selected unary gRPC endpoints as traditional HTTP APIs.

Configuration

builder.Services
    .AddGrpc()
    .AddJsonTranscoding();

Swagger Integration

Swagger is enabled to visualize and test HTTP-mapped unary gRPC endpoints:

builder.Services.AddGrpcSwagger();
builder.Services.AddSwaggerGen();

In development mode:

• Swagger UI is available for HTTP APIs
• gRPC Reflection is enabled for Postman and tooling support

if (app.Environment.IsDevelopment())
{
    app.MapGrpcReflectionService().AllowAnonymous();
    app.UseSwaggerUI();
}

Important Limitations

• ❌ Server-side streaming and bi-directional streaming cannot be exposed via JSON Transcoding
• ❌ Swagger UI does not support streaming gRPC
• ✅ JSON Transcoding is suitable only for unary gRPC

This design keeps streaming endpoints efficient and protocol-pure while still offering REST compatibility where needed.

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🚀 Future Enhancements

• Authentication & authorization for streaming endpoints
• gRPC‑Web support for browser clients
• Redis / Geo‑spatial integration for location queries
• Observability (logging, metrics, tracing)

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📷 Project Architecture

Refer to the attached screenshot for a visual overview of the solution structure and architecture.

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✅ Summary

This POC demonstrates:

• Proper separation of gRPC server and client
• Real‑world usage of all major gRPC patterns
• Practical JSON Transcoding integration
• Streaming‑first design for real‑time systems

It serves as a solid foundation for building production‑grade, real‑time gRPC‑based systems in .NET.