mcp_bridge 0.1.0

Dart plugin for implementing Model Context Protocol (MCP) bridge. Provides tools to build MCP bridge that can expose data, functionality, and interaction patterns to LLM applications.

MCP Bridge

A Dart plugin for bridging between different transport types using the Model Context Protocol (MCP). This package enables you to connect an MCP client and server even if they use different underlying communication protocols (e.g., STDIO, SSE).

Features

• Acts as a bridge between MCP-compatible clients and servers
• Supports multiple transport types:
  • Standard I/O (STDIO)
  • Server-Sent Events (SSE)
• Enables full-duplex message forwarding between client and server
• Auto-reconnection support for client or server failure
• Server shutdown behavior configuration
• JSON-configurable bridge setup
• Designed for local and remote LLM use cases

Use Cases

• Connect a local mcp_server running with STDIO to an external LLM frontend over SSE
• Embed mcp_server inside a Flutter app and expose it via HTTP to AutoGen/ChatGPT
• Bridge CLI-based tools and web-based LLM UIs

Installation

Add the package to your pubspec.yaml:

dependencies:
  mcp_bridge: ^0.1.0

Or install via command line:

dart pub add mcp_bridge

Basic Usage

import 'package:mcp_bridge/mcp_bridge.dart';

void main() async {
  final bridge = McpBridge(
    McpBridgeConfig(
      serverTransportType: 'stdio',
      clientTransportType: 'sse',
      serverConfig: {
        'command': 'dart',
        'arguments': ['my_server.dart'],
      },
      clientConfig: {
        'serverUrl': 'http://localhost:8080/sse',
        'headers': {'Authorization': 'Bearer test_token'},
      },
      serverShutdownBehavior: ServerShutdownBehavior.shutdownBridge,
    ),
  );

  bridge.setAutoReconnect(enabled: true);
  await bridge.initialize();

  print('Bridge is running...');
}

Transport Modes

Standard I/O (STDIO)

Useful for wrapping CLI-based MCP servers or clients:

"serverTransportType": "stdio",
"serverConfig": {
  "command": "dart",
  "arguments": ["my_server.dart"]
}

Server-Sent Events (SSE)

Enables HTTP-based communication between bridge and MCP endpoints:

"clientTransportType": "sse",
"clientConfig": {
  "serverUrl": "http://localhost:8080/sse",
  "headers": {
    "Authorization": "Bearer my_token"
  }
}

Configuration (JSON)

You can load bridge settings from a JSON file using McpBridgeConfig.fromJson(...).

{
  "serverTransportType": "stdio",
  "clientTransportType": "sse",
  "serverShutdownBehavior": "shutdownBridge",
  "serverConfig": {
    "command": "dart",
    "arguments": ["my_server.dart"]
  },
  "clientConfig": {
    "serverUrl": "http://localhost:8080/sse",
    "headers": {
      "Authorization": "Bearer test_token"
    }
  }
}

Logging

You can configure logging behavior using your own logger, or forward logs from client/server for debugging.

final Logger _logger = Logger.getLogger('mcp_bridge');
_logger.setLevel(LogLevel.debug);
_logger.info('Bridge initialized');

Examples

See the example folder for a full example including:

• Bridge setup using STDIO server and SSE client
• Argument parsing with args package
• CLI tool to launch test environments

Future Plans

• ❌ WebSocket transport support
• ❌ Serial port support for embedded systems

Related Packages

• mcp_server: Build and expose an MCP-compatible server
• mcp_client (planned): Connect to any MCP-compliant server

Issues and Feedback

Please file any issues, bugs, or feature requests in our issue tracker.

License

MIT License. See LICENSE for details.