MQTT-Bridge

MQTT-Bridge is a library that allows you to bridge protocols over MQTT, with a focus on gRPC. It provides two implementations:

• Network Bridge: A low-level implementation that allows existing gRPC clients and servers to communicate over MQTT without modification. The network bridge provides a net.Listener and net.Conn interface.
• gRPC Bridge: A higher-level implementation that works directly with MQTT messages while maintaining gRPC-style APIs. The gRPC bridge provides a grpc.ServiceRegistrar and grpc.ServiceInfoProvider interface.

In theory, the network bridge should work with anything that uses the net.Listener and net.Conn interfaces, such as HTTP servers and other networking libraries.

Example Overview

This example demonstrates how to use mqtt-bridge to enable gRPC-style communication over MQTT. The project includes two different implementations showing how to bridge gRPC and MQTT communications.

Overview

The example implements a simple Echo service with three types of RPCs:

• Unary calls (simple request-response)
• Server streaming (server sends multiple responses)
• Bidirectional streaming (both client and server can send multiple messages)

Prerequisites

• Go 1.19 or later
• An MQTT broker (e.g., Mosquitto) running on localhost:1883
• Protocol buffer compiler (protoc)

Service Definition

The Echo service is defined in the proto file:

startLine: 6
endLine: 15

Implementation Options

1. Network Bridge Implementation

The network bridge provides a low-level network implementation that allows existing gRPC clients and servers to communicate over MQTT without modification.

Server Setup

startLine: 34
endLine: 45

Client Setup

startLine: 37
endLine: 55

To run:

# Start the server
go run example/net_bridge/server/main.go

# In another terminal, start the client
go run example/net_bridge/client/main.go

2. gRPC Bridge Implementation

The gRPC bridge provides a higher-level abstraction that works directly with MQTT messages while maintaining gRPC-style APIs.

Server Setup

startLine: 33
endLine: 39

Client Setup

startLine: 30
endLine: 51

To run:

# Start the server
go run example/grpc_bridge/server/main.go

# In another terminal, start the client
go run example/grpc_bridge/client/main.go

Service Implementation

The Echo service implements three types of RPCs:

1. Unary Call - Simple request-response:

startLine: 23
endLine: 33

2. Server Streaming - Server sends multiple responses:

startLine: 36
endLine: 55

3. Bidirectional Streaming - Both sides can send messages:

startLine: 58
endLine: 82

Key Features

• Seamless conversion between gRPC and MQTT communication
• Support for all gRPC communication patterns:
  • Unary calls
  • Server streaming
  • Client streaming
  • Bidirectional streaming
• Automatic message framing and protocol handling
• Integration with existing gRPC tooling
• Choice between network-level and message-level implementations

Notes

• The network bridge implementation is ideal when you want to use existing gRPC code over MQTT
• The gRPC bridge implementation is better when you want to work directly with MQTT messages while maintaining gRPC-style APIs
• Both implementations support the full range of gRPC features
• Ensure your MQTT broker is properly configured and accessible before running the examples
• The gRPC bridge implementation has not been tested for streaming RPCs, only unary has been tested as of now.

License

MIT License

Copyright

Copyright 2024 Golain Systems Private Limited.