mcp-http-server

MCP HTTP Server

A high performance HTTP+SSE Server with Request Headers for MCP Server.

Features

• HTTP/SSE Transport: Support for both HTTP POST and Server-Sent Events
• Flexible Routing: Configurable endpoint paths and prefixes
• Request Headers: Access to HTTP headers in MCP server context
• Multiple Transports: Both stateful and stateless modes
• Middleware Support: Custom middleware for authentication, logging, etc.

Install

npm i mcp-http-server -S

Quick Start

import { startSseAndStreamableHttpMcpServer } from 'mcp-http-server';
import { createServer } from './server.js';

await startSseAndStreamableHttpMcpServer({
  port: 3000,
  createMcpServer: async (params) => {
    console.log('Request headers:', params.headers);
    return createServer();
  },
});

API Reference

startSseAndStreamableHttpMcpServer(params)

Parameters

Parameter	Type	Description
port	number	Port to listen on (default: 8080)
host	string	Host to bind to (default: '::')
stateless	boolean	Enable stateless mode for streamable HTTP (default: true)
middlewares	MiddlewareFunction[]	Custom Express middlewares
routes	RoutesConfig	Custom route configuration
logger	Logger	Custom logger instance
createMcpServer	function	Factory function to create MCP server instances

Route Configuration

The server supports flexible route configuration through the routes parameter.

Default Routes

By default, the server uses the following routes:

{
  prefix: '/',      // Route prefix for all endpoints
  mcp: '/mcp',      // MCP endpoint path
  message: '/message', // Message endpoint path for SSE
  sse: '/sse'       // SSE endpoint path
}

This creates the following endpoints:

• POST /mcp - MCP HTTP transport
• GET /mcp - Returns 405 (Method Not Allowed) or SSE stream
• GET /sse - SSE connection endpoint
• POST /message - SSE message endpoint

Custom Routes

You can customize routes using the routes configuration:

await startSseAndStreamableHttpMcpServer({
  port: 3000,
  routes: {
    prefix: '/api/v1',
    mcp: '/custom-mcp',
    message: '/custom-message',
    sse: '/custom-sse'
  },
  createMcpServer: async () => createServer(),
});

This creates endpoints at:

• POST /api/v1/custom-mcp - MCP HTTP transport
• GET /api/v1/custom-mcp - Returns 405 or SSE stream
• GET /api/v1/custom-sse - SSE connection endpoint
• POST /api/v1/custom-message - SSE message endpoint

Route Configuration Options

routes.prefix

• Type: string
• Default: '/'
• Description: Route prefix for all endpoints

routes.mcp

• Type: string
• Default: '/mcp'
• Description: MCP endpoint path (relative to prefix)

routes.message

• Type: string
• Default: '/message'
• Description: Message endpoint path for SSE (relative to prefix)

routes.sse

• Type: string
• Default: '/sse'
• Description: SSE endpoint path (relative to prefix)

Path Handling

The server automatically handles leading/trailing slashes in paths:

// These configurations are equivalent:
routes: {
  prefix: '/api/v2/',
  mcp: 'mcp-endpoint',
  sse: '/sse-endpoint/'
}

routes: {
  prefix: '/api/v2',
  mcp: '/mcp-endpoint',
  sse: 'sse-endpoint'
}

Both result in:

• /api/v2/mcp-endpoint
• /api/v2/sse-endpoint/

Usage Examples

Basic HTTP Server

import { startSseAndStreamableHttpMcpServer } from 'mcp-http-server';
import { Server } from '@modelcontextprotocol/sdk/server/index.js';

const server = await startSseAndStreamableHttpMcpServer({
  port: 3000,
  createMcpServer: async () => {
    return new Server(
      { name: 'my-server', version: '1.0.0' },
      { capabilities: { tools: {} } }
    );
  },
});

console.log(`Server running at ${server.url}`);

With Custom Routes and Middleware

import { startSseAndStreamableHttpMcpServer } from 'mcp-http-server';

const authMiddleware = (req, res, next) => {
  const token = req.headers.authorization;
  if (!token) {
    return res.status(401).json({ error: 'Unauthorized' });
  }
  next();
};

await startSseAndStreamableHttpMcpServer({
  port: 3000,
  host: 'localhost',
  routes: {
    prefix: '/api/v1',
    mcp: '/mcp',
    sse: '/events'
  },
  middlewares: [authMiddleware],
  createMcpServer: async (context) => {
    console.log('User agent:', context.headers['user-agent']);
    return createServer();
  },
});

Command Line Interface

import { program } from 'commander';
import { StdioServerTransport } from '@modelcontextprotocol/sdk/server/stdio.js';

program
  .name('mcp-server')
  .description('MCP server with HTTP and stdio support')
  .version('1.0.0')
  .option('--host <host>', 'host to bind server to')
  .option('--port <port>', 'port to listen on for HTTP transport')
  .option('--prefix <prefix>', 'route prefix for HTTP endpoints', '/api')
  .action(async (options) => {
    try {
      if (options.port || options.host) {
        // HTTP/SSE transport
        await startSseAndStreamableHttpMcpServer({
          host: options.host,
          port: options.port ? parseInt(options.port) : undefined,
          routes: {
            prefix: options.prefix,
          },
          createMcpServer: async (params) => {
            console.log('HTTP request from:', params.headers['user-agent']);
            return createServer();
          },
        });
      } else {
        // Stdio transport
        const server = createServer();
        const transport = new StdioServerTransport();
        await server.connect(transport);
        console.debug('MCP Server running on stdio');
      }
    } catch (error) {
      console.error('Error:', error);
      process.exit(1);
    }
  });

program.parse();

Transport Modes

Stateful Mode (Default: Stateless)

await startSseAndStreamableHttpMcpServer({
  stateless: false, // Enable stateful mode
  createMcpServer: async () => createServer(),
});

In stateful mode:

• Each client gets a unique session ID
• Sessions are maintained across requests
• Requires proper session cleanup

Stateless Mode (Recommended)

await startSseAndStreamableHttpMcpServer({
  stateless: true, // Default
  createMcpServer: async () => createServer(),
});

In stateless mode:

• No session state maintained
• Each request is independent
• Better for scaling and reliability

Return Value

startSseAndStreamableHttpMcpServer returns a McpServerEndpoint object:

interface McpServerEndpoint {
  url: string;      // Full URL to MCP endpoint
  sseUrl: string;   // Full URL to SSE endpoint
  port: number;     // Server port
  close: () => void; // Function to close server
}

Example:

const endpoint = await startSseAndStreamableHttpMcpServer({
  port: 3000,
  routes: { prefix: '/api' },
  createMcpServer: async () => createServer(),
});

console.log('MCP endpoint:', endpoint.url);     // http://localhost:3000/api/mcp
console.log('SSE endpoint:', endpoint.sseUrl);  // http://localhost:3000/api/sse

// Gracefully shutdown
process.on('SIGTERM', () => {
  endpoint.close();
});

License

MIT