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mattzcareymattzcarey
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feat: fetch transport
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‎package-lock.json‎

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‎package.json‎

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},
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"devDependencies": {
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"@cfworker/json-schema": "^4.1.1",
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"@hono/node-server": "^1.19.6",
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"hono": "^4.10.7",
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"@eslint/js": "^9.39.1",
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"@types/content-type": "^1.1.8",
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"@types/cors": "^2.8.17",

‎src/examples/server/honoFetchStreamableHttp.ts‎

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/**
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* Example MCP Server using Hono.js with FetchStreamableHTTPServerTransport
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*
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* This example demonstrates how to use the experimental FetchStreamableHTTPServerTransport
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* with Hono.js to create an MCP server that uses Web Standard APIs.
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*
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* The FetchStreamableHTTPServerTransport uses Web Standard Request/Response objects,
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* making it compatible with various runtimes like Cloudflare Workers, Deno, Bun, etc.
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* This example runs on Node.js using @hono/node-server.
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*
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* To run this example:
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* npx tsx src/examples/server/honoFetchStreamableHttp.ts
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*
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* Then test with curl:
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* # Initialize
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* curl -X POST http://localhost:3000/mcp \
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* -H "Content-Type: application/json" \
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* -H "Accept: application/json, text/event-stream" \
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* -d '{"jsonrpc":"2.0","method":"initialize","params":{"protocolVersion":"2025-03-26","clientInfo":{"name":"test","version":"1.0"},"capabilities":{}},"id":1}'
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*
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* # List tools (use session ID from init response)
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* curl -X POST http://localhost:3000/mcp \
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* -H "Content-Type: application/json" \
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* -H "Accept: application/json, text/event-stream" \
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* -H "mcp-session-id: <session-id>" \
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* -d '{"jsonrpc":"2.0","method":"tools/list","params":{},"id":2}'
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*/
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import { Hono } from 'hono';
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import { cors } from 'hono/cors';
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import { serve } from '@hono/node-server';
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import { McpServer } from '../../server/mcp.js';
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import { FetchStreamableHTTPServerTransport, type AuthenticatedRequest } from '../../experimental/fetch-streamable-http/index.js';
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import { CallToolResult, GetPromptResult, ReadResourceResult } from '../../types.js';
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import { z } from 'zod';
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// Create the Hono app
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const app = new Hono();
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// Store active transports by session ID for session management
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const transports = new Map<string, FetchStreamableHTTPServerTransport>();
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/**
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* Creates and configures an MCP server with example tools, resources, and prompts
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*/
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function createMcpServer(): McpServer {
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const server = new McpServer(
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{
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name: 'hono-fetch-streamable-http-server',
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version: '1.0.0'
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},
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{ capabilities: { logging: {} } }
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);
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// Register a simple tool using the new registerTool API
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server.registerTool(
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'greet',
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{
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description: 'Greets someone by name',
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inputSchema: {
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name: z.string().describe('The name to greet')
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}
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},
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async ({ name }): Promise<CallToolResult> => {
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return {
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content: [
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{
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type: 'text',
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text: `Hello, ${name}! Welcome to the Hono MCP server.`
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}
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]
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};
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}
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);
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// Register a tool that demonstrates async operations
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server.registerTool(
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'calculate',
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{
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description: 'Performs a simple calculation',
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inputSchema: {
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operation: z.enum(['add', 'subtract', 'multiply', 'divide']).describe('The operation to perform'),
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a: z.number().describe('First operand'),
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b: z.number().describe('Second operand')
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}
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},
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async ({ operation, a, b }): Promise<CallToolResult> => {
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let result: number;
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switch (operation) {
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case 'add':
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result = a + b;
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break;
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case 'subtract':
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result = a - b;
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break;
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case 'multiply':
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result = a * b;
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break;
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case 'divide':
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if (b === 0) {
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return {
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content: [{ type: 'text', text: 'Error: Division by zero' }],
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isError: true
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};
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}
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result = a / b;
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break;
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}
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return {
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content: [
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{
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type: 'text',
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text: `${a} ${operation} ${b} = ${result}`
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}
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]
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};
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}
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);
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// Register a tool that sends notifications (demonstrates SSE streaming)
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server.registerTool(
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'send-notifications',
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{
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description: 'Sends a series of notifications to demonstrate SSE streaming',
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inputSchema: {
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count: z.number().min(1).max(10).default(3).describe('Number of notifications to send'),
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interval: z.number().min(100).max(2000).default(500).describe('Interval between notifications in ms')
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}
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},
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async ({ count, interval }, extra): Promise<CallToolResult> => {
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const sleep = (ms: number) => new Promise(resolve => setTimeout(resolve, ms));
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for (let i = 1; i <= count; i++) {
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await server.sendLoggingMessage(
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{
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level: 'info',
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data: `Notification ${i} of ${count} at ${new Date().toISOString()}`
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},
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extra.sessionId
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);
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if (i < count) {
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await sleep(interval);
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}
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}
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return {
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content: [
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{
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type: 'text',
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text: `Sent ${count} notifications with ${interval}ms interval`
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}
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]
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};
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}
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);
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// Register a simple prompt using the new registerPrompt API
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server.registerPrompt(
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'code-review',
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{
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description: 'A prompt template for code review',
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argsSchema: {
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language: z.string().describe('Programming language'),
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code: z.string().describe('Code to review')
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}
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},
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async ({ language, code }): Promise<GetPromptResult> => {
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return {
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messages: [
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{
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role: 'user',
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content: {
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type: 'text',
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text: `Please review the following ${language} code and provide feedback on:
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1. Code quality and best practices
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2. Potential bugs or issues
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3. Performance considerations
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4. Suggestions for improvement
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Code:
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\`\`\`${language}
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${code}
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\`\`\``
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}
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}
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]
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};
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}
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);
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// Register a simple resource using the new registerResource API
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server.registerResource(
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'server-info',
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'mcp://server/info',
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{
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description: 'Information about this MCP server',
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mimeType: 'application/json'
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},
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async (): Promise<ReadResourceResult> => {
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return {
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contents: [
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{
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uri: 'mcp://server/info',
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mimeType: 'application/json',
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text: JSON.stringify(
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{
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name: 'hono-fetch-streamable-http-server',
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version: '1.0.0',
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runtime: 'Node.js',
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framework: 'Hono',
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transport: 'FetchStreamableHTTPServerTransport',
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timestamp: new Date().toISOString()
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},
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null,
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2
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)
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}
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]
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};
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}
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);
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return server;
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}
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// Configure CORS middleware for all routes
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app.use(
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'*',
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cors({
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origin: '*',
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allowMethods: ['GET', 'POST', 'DELETE', 'OPTIONS'],
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allowHeaders: ['Content-Type', 'Accept', 'mcp-session-id', 'last-event-id', 'mcp-protocol-version'],
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exposeHeaders: ['mcp-session-id']
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})
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);
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app.all('/mcp', async c => {
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const request = c.req.raw as AuthenticatedRequest;
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// Check for existing session
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const sessionId = request.headers.get('mcp-session-id');
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if (sessionId && transports.has(sessionId)) {
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// Reuse existing transport for this session
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const transport = transports.get(sessionId)!;
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return transport.handleRequest(request);
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}
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// For new sessions or initialization, create new transport and server
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const server = createMcpServer();
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const transport = new FetchStreamableHTTPServerTransport({
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sessionIdGenerator: () => crypto.randomUUID(),
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onsessioninitialized: sessionId => {
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// Store the transport for session reuse
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transports.set(sessionId, transport);
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console.log(`Session initialized: ${sessionId}`);
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},
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onsessionclosed: sessionId => {
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// Clean up when session closes
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transports.delete(sessionId);
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console.log(`Session closed: ${sessionId}`);
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}
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});
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await server.connect(transport);
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return transport.handleRequest(request);
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});
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// Health check endpoint
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app.get('/health', c => {
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return c.json({
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status: 'healthy',
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activeSessions: transports.size,
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timestamp: new Date().toISOString()
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});
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});
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// Start the server
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const PORT = 3000;
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console.log(`MCP server running at http://localhost:${PORT}/mcp`);
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serve({
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fetch: app.fetch,
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port: PORT
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});
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// Handle graceful shutdown
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process.on('SIGINT', async () => {
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console.log('\nShutting down server...');
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// Close all active transports
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for (const [sessionId, transport] of transports) {
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console.log(`Closing session: ${sessionId}`);
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await transport.close();
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}
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transports.clear();
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console.log('Server stopped.');
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process.exit(0);
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});

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