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ihrprihrpr
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support for server returning json -- not stream
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‎src/examples/README.md

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@@ -6,6 +6,34 @@ This directory contains example implementations of MCP clients and servers using
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Multi node with stete management example will be added soon after we add support.
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### Server with JSON response mode (`server/jsonResponseStreamableHttp.ts`)
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A simple MCP server that uses the Streamable HTTP transport with JSON response mode enabled, implemented with Express. The server provides a simple `greet` tool that returns a greeting for a name.
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#### Running the server
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```bash
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npx tsx src/examples/server/jsonResponseStreamableHttp.ts
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```
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The server will start on port 3000. You can test the initialization and tool calling:
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```bash
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# Initialize the server and get the session ID from headers
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SESSION_ID=$(curl -X POST -H "Content-Type: application/json" -H "Accept: application/json" \
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-d '{"jsonrpc":"2.0","method":"initialize","params":{"capabilities":{}},"id":"1"}' \
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-i http://localhost:3000/mcp 2>&1 | grep -i "mcp-session-id" | cut -d' ' -f2 | tr -d '\r')
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echo "Session ID: $SESSION_ID"
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# Call the greet tool using the saved session ID
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curl -X POST -H "Content-Type: application/json" -H "Accept: application/json" \
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-H "mcp-session-id: $SESSION_ID" \
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-d '{"jsonrpc":"2.0","method":"mcp.call_tool","params":{"name":"greet","arguments":{"name":"World"}},"id":"2"}' \
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http://localhost:3000/mcp
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```
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Note that in this example, we're using plain JSON response mode by setting `Accept: application/json` header.
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### Server (`server/simpleStreamableHttp.ts`)
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A simple MCP server that uses the Streamable HTTP transport, implemented with Express. The server provides:

‎src/examples/client/simpleStreamableHttp.ts

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@@ -15,9 +15,9 @@ import {
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async function main(): Promise<void> {
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// Create a new client with streamable HTTP transport
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const client = new Client({
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name: 'example-client',
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version: '1.0.0'
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const client = new Client({
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name: 'example-client',
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version: '1.0.0'
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});
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const transport = new StreamableHTTPClientTransport(
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new URL('http://localhost:3000/mcp')
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await client.connect(transport);
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console.log('Connected to MCP server');
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// List available tools
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const toolsRequest: ListToolsRequest = {
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method: 'tools/list',
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console.log('Greeting result:', greetResult.content[0].text);
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// List available prompts
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const promptsRequest: ListPromptsRequest = {
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method: 'prompts/list',
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params: {}
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};
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const promptsResult = await client.request(promptsRequest, ListPromptsResultSchema);
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console.log('Available prompts:', promptsResult.prompts);
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try {
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const promptsRequest: ListPromptsRequest = {
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method: 'prompts/list',
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params: {}
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};
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const promptsResult = await client.request(promptsRequest, ListPromptsResultSchema);
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console.log('Available prompts:', promptsResult.prompts);
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} catch (error) {
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console.log(`Prompts not supported by this server (${error})`);
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}
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// Get a prompt
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const promptRequest: GetPromptRequest = {
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method: 'prompts/get',
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params: {
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name: 'greeting-template',
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arguments: { name: 'MCP User' }
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}
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};
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const promptResult = await client.request(promptRequest, GetPromptResultSchema);
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console.log('Prompt template:', promptResult.messages[0].content.text);
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try {
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const promptRequest: GetPromptRequest = {
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method: 'prompts/get',
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params: {
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name: 'greeting-template',
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arguments: { name: 'MCP User' }
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}
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};
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const promptResult = await client.request(promptRequest, GetPromptResultSchema);
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console.log('Prompt template:', promptResult.messages[0].content.text);
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} catch (error) {
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console.log(`Prompt retrieval not supported by this server (${error})`);
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}
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// List available resources
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const resourcesRequest: ListResourcesRequest = {
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method: 'resources/list',
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params: {}
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};
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const resourcesResult = await client.request(resourcesRequest, ListResourcesResultSchema);
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console.log('Available resources:', resourcesResult.resources);
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try {
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const resourcesRequest: ListResourcesRequest = {
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method: 'resources/list',
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params: {}
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};
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const resourcesResult = await client.request(resourcesRequest, ListResourcesResultSchema);
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console.log('Available resources:', resourcesResult.resources);
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} catch (error) {
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console.log(`Resources not supported by this server (${error})`);
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}
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// Close the connection
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await client.close();
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}

‎src/examples/server/jsonResponseStreamableHttp.ts

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import express, { Request, Response } from 'express';
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import { randomUUID } from 'node:crypto';
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import { McpServer } from '../../server/mcp.js';
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import { StreamableHTTPServerTransport } from '../../server/streamableHttp.js';
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import { z } from 'zod';
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import { CallToolResult } from '../../types.js';
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// Create an MCP server with implementation details
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const server = new McpServer({
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name: 'json-response-streamable-http-server',
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version: '1.0.0',
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});
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// Register a simple tool that returns a greeting
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server.tool(
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'greet',
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'A simple greeting tool',
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{
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name: z.string().describe('Name to greet'),
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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}!`,
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},
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],
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};
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}
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);
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const app = express();
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app.use(express.json());
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// Map to store transports by session ID
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const transports: { [sessionId: string]: StreamableHTTPServerTransport } = {};
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app.post('/mcp', async (req: Request, res: Response) => {
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console.log('Received MCP request:', req.body);
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try {
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// Check for existing session ID
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const sessionId = req.headers['mcp-session-id'] as string | undefined;
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let transport: StreamableHTTPServerTransport;
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if (sessionId && transports[sessionId]) {
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// Reuse existing transport
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transport = transports[sessionId];
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} else if (!sessionId && isInitializeRequest(req.body)) {
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// New initialization request - use JSON response mode
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transport = new StreamableHTTPServerTransport({
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sessionIdGenerator: () => randomUUID(),
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enableJsonResponse: true, // Enable JSON response mode
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});
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// Connect the transport to the MCP server BEFORE handling the request
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await server.connect(transport);
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// After handling the request, if we get a session ID back, store the transport
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await transport.handleRequest(req, res, req.body);
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// Store the transport by session ID for future requests
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if (transport.sessionId) {
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transports[transport.sessionId] = transport;
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}
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return; // Already handled
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} else {
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// Invalid request - no session ID or not initialization request
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res.status(400).json({
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jsonrpc: '2.0',
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error: {
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code: -32000,
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message: 'Bad Request: No valid session ID provided',
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},
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id: null,
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});
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return;
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}
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// Handle the request with existing transport - no need to reconnect
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await transport.handleRequest(req, res, req.body);
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} catch (error) {
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console.error('Error handling MCP request:', error);
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if (!res.headersSent) {
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res.status(500).json({
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jsonrpc: '2.0',
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error: {
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code: -32603,
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message: 'Internal server error',
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},
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id: null,
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});
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}
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}
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});
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// Helper function to detect initialize requests
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function isInitializeRequest(body: unknown): boolean {
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if (Array.isArray(body)) {
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return body.some(msg => typeof msg === 'object' && msg !== null && 'method' in msg && msg.method === 'initialize');
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}
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return typeof body === 'object' && body !== null && 'method' in body && body.method === 'initialize';
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}
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// Start the server
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const PORT = 3000;
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app.listen(PORT, () => {
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console.log(`MCP Streamable HTTP Server with JSON responses listening on port ${PORT}`);
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console.log(`Server is running. Press Ctrl+C to stop.`);
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console.log(`Initialize with: curl -X POST -H "Content-Type: application/json" -H "Accept: application/json" -d '{"jsonrpc":"2.0","method":"initialize","params":{"capabilities":{}},"id":"1"}' http://localhost:${PORT}/mcp`);
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console.log(`Then call tool with: curl -X POST -H "Content-Type: application/json" -H "Accept: application/json" -H "mcp-session-id: YOUR_SESSION_ID" -d '{"jsonrpc":"2.0","method":"mcp.call_tool","params":{"name":"greet","arguments":{"name":"World"}},"id":"2"}' http://localhost:${PORT}/mcp`);
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});
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// Handle server shutdown
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process.on('SIGINT', async () => {
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console.log('Shutting down server...');
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await server.close();
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process.exit(0);
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});

‎src/server/.streamableHttp.test.ts.swp

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