@reaatech/mcp-server-transport

Status: Pre-1.0 — APIs may change in minor versions. Pin to a specific version in production.

MCP transport implementations (Streamable HTTP, SSE) with session management. Mounts MCP transport handlers onto an Express application, managing session lifecycle, automatic cleanup, and transport-level metrics.

Installation

npm install @reaatech/mcp-server-transport
# or
pnpm add @reaatech/mcp-server-transport

Feature Overview

• Streamable HTTP transport — Primary transport via POST /mcp, session-aware via Mcp-Session-Id header
• SSE transport — Legacy transport via GET /mcp/sse + POST /mcp/messages
• Session lifecycle — Creates, reuses, and cleans up MCP sessions per transport
• Automatic cleanup — Periodic eviction of expired sessions based on SESSION_TIMEOUT_MS
• Transport metrics — Records request counts and active session gauges via @reaatech/mcp-server-observability

Quick Start

import express from 'express';
import { mountStreamableHTTP, mountSSE } from '@reaatech/mcp-server-transport';
import { createMcpServer, getTools } from '@reaatech/mcp-server-engine';
 
const app = express();
app.use(express.json());
 
const serverFactory = () => createMcpServer(getTools());
 
// Primary transport: StreamableHTTP
mountStreamableHTTP(app, serverFactory);
 
// Legacy transport: SSE
mountSSE(app, serverFactory);
 
app.listen(8080);

API Reference

mountStreamableHTTP(app, serverFactory)

Mounts the Streamable HTTP transport on an Express application.

import { mountStreamableHTTP } from '@reaatech/mcp-server-transport';
 
mountStreamableHTTP(app, () => createMcpServer(tools));

Endpoints

Session Behavior

• New sessions: Created when no Mcp-Session-Id header is present. Server manages a per-session StreamableHTTPServerTransport and McpServer instance.
• Session reuse: Existing sessions are reused when a matching Mcp-Session-Id header is provided.
• Cleanup: Sessions idle longer than SESSION_TIMEOUT_MS are automatically closed and removed.

mountSSE(app, serverFactory)

Mounts the SSE (Server-Sent Events) transport on an Express application.

import { mountSSE } from '@reaatech/mcp-server-transport';
 
mountSSE(app, () => createMcpServer(tools));

Endpoints

SSE Headers

• Content-Type: text/event-stream
• Cache-Control: no-cache
• Connection: keep-alive
• X-Accel-Buffering: no — for nginx reverse proxy compatibility

clearAllSessions() / clearAllSSESessions()

Clear all active sessions. Primarily for testing.

import { clearAllSessions, clearAllSSESessions } from '@reaatech/mcp-server-transport';
 
clearAllSessions();    // Clear StreamableHTTP sessions
clearAllSSESessions(); // Clear SSE sessions

updateTransportSessionCount(transport, count)

Update the active session gauge for a transport type. Called internally by session lifecycle hooks.

import { updateTransportSessionCount } from '@reaatech/mcp-server-transport';
 
updateTransportSessionCount('streamable-http', 42);
updateTransportSessionCount('sse', 7);

Configuration

Uses environment variables from @reaatech/mcp-server-core:

Integration with the Server

The @reaatech/mcp-server-engine package mounts both transports automatically when you use createApp():

import { createApp } from '@reaatech/mcp-server-engine';
 
const app = await createApp();
// StreamableHTTP mounted at POST /mcp, DELETE /mcp
// SSE mounted at GET /mcp/sse, POST /mcp/messages
 
app.listen(8080);

Related Packages

• @reaatech/mcp-server-core — Configuration and types
• @reaatech/mcp-server-observability — Transport metrics
• @reaatech/mcp-server-engine — MCP server framework

License

MIT