Transport Overview

MCP Framework supports multiple transport mechanisms for communication between the client and server. Each transport type has its own characteristics, advantages, and use cases.

Available Transports

The framework currently supports the following transport types:

• STDIO Transport: The default transport that uses standard input/output streams
• HTTP Stream Transport: Streamable HTTP transport that implements the MCP 2025-11-25 specification
• Serverless (Lambda): Stateless request handling for AWS Lambda, Cloudflare Workers, and other serverless platforms
• SSE Transport: DEPRECATED - Server-Sent Events based transport that has been replaced by HTTP Stream Transport

Comparison

Choosing a Transport

Choose your transport based on your application's needs:

• Use STDIO Transport when:

  • Building CLI tools
  • Need direct process communication
  • Working with local integrations
  • Want minimal configuration

• Use HTTP Stream Transport when:

  • Building web applications
  • Need network-based communication
  • Require authentication or session management
  • Want to support multiple clients
  • Need resumable connections
  • Need to scale horizontally
  • Require compliance with latest MCP specification

• Use Serverless (Lambda) when:

  • Deploying on AWS Lambda, Cloudflare Workers, or Vercel Edge
  • Need auto-scaling without managing infrastructure
  • Want pay-per-request pricing
  • Building stateless APIs

• Use SSE Transport only for:

  • Legacy applications that depend on the older transport

Configuration

STDIO Transport (Default)

const server = new MCPServer();
// or explicitly:
const server = new MCPServer({
  transport: { type: "stdio" }
});

HTTP Stream Transport

const server = new MCPServer({
  transport: {
    type: "http-stream",
    options: {
      port: 8080,            // Optional (default: 8080)
      endpoint: "/mcp",      // Optional (default: "/mcp")
      responseMode: "batch", // Optional (default: "batch")
      cors: {
        allowOrigin: "*"     // Optional CORS configuration
      },
      auth: {
        // Optional authentication configuration
      }
    }
  }
});

Serverless (Lambda)

import { MCPServer } from 'mcp-framework';
import { MyTool } from './tools/MyTool.js';

const server = new MCPServer({
  name: 'my-server',
  version: '1.0.0',
});
server.addTool(MyTool);

// AWS Lambda
export const handler = server.createLambdaHandler();

// Cloudflare Workers / generic
export default {
  fetch: (request: Request) => server.handleRequest(request),
};

SSE Transport (Deprecated)

const server = new MCPServer({
  transport: {
    type: "sse",
    options: {
      port: 8080,            // Optional (default: 8080)
      endpoint: "/sse",      // Optional (default: "/sse")
      messageEndpoint: "/messages", // Optional (default: "/messages")
      auth: {
        // Optional authentication configuration
      }
    }
  }
});

Transport Security Features

Both the HTTP Stream and SSE transports include security features introduced in MCP spec 2025-11-25:

• Host Binding: Servers bind to 127.0.0.1 (localhost only) by default. Set host: '0.0.0.0' to accept remote connections when deploying in Docker or cloud environments.
• Origin Validation: Configure allowedOrigins in the cors block to validate the Origin header on every request, protecting against DNS rebinding attacks. Non-browser clients (without an Origin header) are allowed through. See the individual transport pages for full configuration details.

Multi-Transport

You can run multiple transports simultaneously from a single server instance using the transports array config. This is useful when you need to serve both local clients (via stdio) and remote clients (via HTTP) at the same time:

const server = new MCPServer({
  transports: [
    { type: "stdio" },
    { type: "http-stream", options: { port: 8080 } },
  ],
});

Tools, prompts, and resources are loaded once and shared across all transports. See Multi-Transport for full details.

For detailed information about each transport type, see:

• Multi-Transport - Running multiple transports concurrently
• STDIO Transport
• HTTP Stream Transport
• Serverless (Lambda)
• SSE Transport (Deprecated)