Simple Streamable HTTP MCP Server

A clean implementation of an MCP server using the Streamable HTTP transport, following the official MCP patterns.

Features

• Streamable HTTP Transport: Supports both JSON responses and Server-Sent Events (SSE)

• Session Management: Proper session handling with unique session IDs

• Progress Notifications: Long-running tools send progress updates

• Multiple Tools:

  • hello_world: Simple greeting tool

  • get_server_info: Returns server information

  • long_running_test: Configurable duration test with progress (default: 30s)

  • slow_test: 10-minute test with progress updates

Related MCP server: Mock MCP Server

Architecture

This server follows the MCP team's recommended patterns:

1. Session-based Architecture: Each client gets a unique session ID

2. Transport Reuse: Transports are stored and reused for subsequent requests

3. Proper Initialization: New sessions are created only on initialization requests

4. Clean Shutdown: All transports are properly closed on server shutdown

Running the Server

# Install dependencies
npm ci

# Run the server (default port: 3001, DEBUG logging enabled by default)
npm run start

# Run without debug logging, or edit `.env` to set DEBUG=false
DEBUG=false npm run start

# Run in development mode (auto-reload)
npm run dev

Testing

Use the provided test script to verify the server is working correctly:

npm run test:http

This will test:

• Session initialization

• Tool listing and calling

• Session ID management

• SSE streaming

• Session termination

Progress Notifications

The long_running_test and slow_test tools demonstrate progress notifications:

// Example tool call with progress
{
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "name": "long_running_test",
    "arguments": {
      "duration": 60,
      "steps": 12,
      "message": "Testing progress notifications"
    },
    "_meta": {
      "progressToken": "unique-progress-token"
    }
  },
  "id": 1
}

The server will send progress notifications:

{
  "method": "notifications/progress",
  "params": {
    "progress": 1,
    "total": 12,
    "progressToken": "unique-progress-token"
  }
}

Key Differences from Basic Examples

1. Proper Session Management: Sessions are created per client, not per request

2. Transport Lifecycle: Transports persist across requests within a session

3. Error Handling: Comprehensive error handling for all edge cases

4. Progress Support: Long-running operations can report progress

5. Clean Architecture: Clear separation between server creation and request handling

Environment Variables

• PORT: Server port (default: 3001)

• DEBUG: Enable debug logging (true by default)

Endpoints

• POST /mcp: Handle JSON-RPC requests

• GET /mcp: Handle SSE streaming

• DELETE /mcp: Terminate sessions

• GET /health: Health check endpoint