MCP SSE Server POC

A proof-of-concept server for STDIO transport of Model Context Protocol (MCP) into instant Server-Sent Events (SSE) streaming, deployable as a service. Instant remote hosted MCP servers with zero infrastructure work.

Features

• Create and manage MCP server configurations via a simple UI

• Generate stable SSE endpoints for each configuration

• Stream real-time model responses via SSE

• Built with Express, Drizzle ORM, and PostgreSQL

• One-click deployment on Render

Related MCP server: MCP Server Template

Local Development

Prerequisites

• Node.js (v18 or later)

• PostgreSQL database

Setup

1. Clone this repository:

git clone https://github.com/yourusername/mcp-sse-poc.git
cd mcp-sse-poc

2. Install dependencies:

npm install

3. Set up your local PostgreSQL database and create a .env file with your database connection string:

DATABASE_URL=postgresql://username:password@localhost:5432/mcp_sse_db

4. Generate and run migrations:

npm run generate
npm run migrate

5. Start the development server:

npm run dev

6. Open your browser and navigate to http://localhost:3000

Deployment on Render

1. Push Your Code to GitHub/GitLab

Make sure your repository includes all the files in this project.

2. Create a Web Service on Render

1. Log in to your Render Dashboard

2. Click New → Web Service

3. Connect your GitHub/GitLab repository

4. Configure the service:

   • Name: Choose a name (e.g., mcp-sse-poc)

   • Environment: Node

   • Build Command: npm install (this will trigger the postinstall script that builds and migrates)

   • Start Command: npm start

5. Click Create Web Service

3. Add a PostgreSQL Database

1. In Render, click New → PostgreSQL Database

2. Name it (e.g., mcp-sse-db)

3. Select the free plan

4. Click Create Database

5. Copy the provided DATABASE_URL connection string

4. Configure Environment Variables

1. Go back to your Web Service

2. Navigate to the Environment tab

3. Add the following environment variable:

   • Key: DATABASE_URL

   • Value: Paste the connection string you copied

5. Deploy

Render will automatically deploy your application. Once deployed, you can access it at the URL provided by Render.

Usage

1. Open your deployed application in a browser

2. Create a new MCP server configuration by entering a name and JSON configuration

3. Save the configuration to generate an SSE URL

4. Use the SSE URL in your client application to stream model responses

Example Configuration

{
  "mcpServers": {
    "playwright": {
      "command": "npx",
      "args": ["@playwright/mcp@latest"]
    }
  }
}

Model Context Protocol (MCP)

The Model Context Protocol is a lightweight, STDIO-based specification for interacting with language models over a standard input/output interface. It allows for real-time streaming of model responses and is designed to be simple and extensible.

Core Concepts

1. STDIO Transport

   • Input: JSON blob describing context messages

   • Output: Incremental response tokens streamed to stdout

   • Errors & Events: Non-blocking notifications on stderr

2. JSON Message Format

   {
     "context": [
       { "role": "system", "content": "You are a helpful assistant." },
       { "role": "user", "content": "Translate to French: Hello, world!" }
     ],
     "stream": true
   }

3. Server-Sent Events (SSE)

   • Each JSON chunk becomes an SSE event

   • Perfect mapping to MCP's unidirectional streaming model

License

MIT