@tylercoles/mcp-transport-sse

Server-Sent Events (SSE) transport for MCP servers. This transport provides backwards compatibility with the deprecated HTTP+SSE transport from MCP protocol version 2024-11-05.

Installation

npm install @tylercoles/mcp-transport-sse

Usage

import { MCPServer } from "@tylercoles/mcp-server";
import { createSSEServer } from "@tylercoles/mcp-transport-sse";

// Create MCP server
const server = new MCPServer({
  name: "my-server",
  version: "1.0.0"
});

// Register tools, resources, prompts...
server.registerTool("hello", {
  description: "Say hello",
  inputSchema: { name: z.string() }
}, async ({ name }) => ({
  content: [{ type: "text", text: `Hello, ${name}!` }]
}));

// Create and use SSE transport
const transport = createSSEServer(server, {
  port: 3000,
  host: "127.0.0.1",
  basePath: "/",
  cors: true
});

// Start the server
await server.start();

Configuration

The SSE transport accepts the following configuration options:

• port (number): Port to listen on (default: 3000)
• host (string): Host to bind to (default: "127.0.0.1")
• basePath (string): Base path for endpoints (default: "/")
• cors (object | false): CORS configuration (default: enabled with permissive settings)
• enableDnsRebindingProtection (boolean): Enable DNS rebinding protection (default: true)
• allowedHosts (string[]): Allowed hosts for DNS rebinding protection (default: ["127.0.0.1", "localhost"])

Endpoints

The SSE transport exposes the following endpoints:

• GET {basePath}/sse - SSE stream for server-to-client messages
• POST {basePath}/messages?sessionId={id} - Client-to-server messages
• GET {basePath}/health - Health check endpoint

Security

This transport includes:

• DNS rebinding protection (enabled by default)
• CORS support
• Request size limits
• Session management

Backwards Compatibility

This transport is designed to work with older MCP clients that expect the HTTP+SSE transport pattern. For new implementations, consider using the Streamable HTTP transport instead.

License

MIT