JSON RPC Protocol

A simple yet complete implementation of a JSON-RPC 2.0 real-time server using Node.js and Express, with a vanilla JavaScript frontend client.

📋 Project Overview

This project demonstrates a modern JSON-RPC 2.0 implementation with:

• Backend: Express.js server implementing JSON-RPC 2.0 specification
• Frontend: Vanilla HTML/CSS/JavaScript client (no frameworks)
• Protocol: JSON-RPC 2.0 (https://www.jsonrpc.org/specification)

Available Methods

The server provides three time-related RPC methods:

1. getCurrentTime - Returns current server time in ISO 8601 format
2. getTimeZone - Returns server timezone name and UTC offset
3. getUnixTimestamp - Returns current Unix timestamp in seconds

🚀 Quick Start

Prerequisites

• Node.js (v12 or higher)
• npm

Installation

cd d:\PROJECTS\JSON-RPC-Protocol
npm install

Running the Server

npm start

The server will start on http://localhost:3000 with the following endpoints:

• RPC Endpoint: POST http://localhost:3000/rpc
• Health Check: GET http://localhost:3000/health
• Server Info: GET http://localhost:3000/

Opening the Client

1. Open index.html in your web browser
2. Click any of the three buttons to send RPC requests
3. View formatted JSON responses

📚 API Documentation

Base URL

http://localhost:3000/rpc

Request Format (JSON-RPC 2.0)

{
  "jsonrpc": "2.0",
  "method": "methodName",
  "params": {},
  "id": 1
}

Parameters:

• jsonrpc (string, required): Must be exactly "2.0"
• method (string, required): Name of the method to call
• params (object, optional): Method parameters (empty object if no params needed)
• id (number/string, required): Unique request identifier for matching responses

Response Format

Success Response

{
  "jsonrpc": "2.0",
  "result": { /* result data */ },
  "id": 1
}

Error Response

{
  "jsonrpc": "2.0",
  "error": {
    "code": -32601,
    "message": "Method not found",
    "data": "Additional error details"
  },
  "id": 1
}

Error Codes

Code	Message	Description
-32700	Parse error	Invalid JSON was received
-32600	Invalid Request	Request structure is invalid
-32601	Method not found	Called method doesn't exist
-32602	Invalid params	Method parameters are invalid
-32603	Internal error	Internal server error

🔧 Available Methods

1. getCurrentTime

Returns the current server time in ISO 8601 format.

Request:

{
  "jsonrpc": "2.0",
  "method": "getCurrentTime",
  "params": {},
  "id": 1
}

Response:

{
  "jsonrpc": "2.0",
  "result": {
    "timestamp": "2026-01-11T10:30:45.123Z"
  },
  "id": 1
}

2. getTimeZone

Returns the server's timezone information including name and UTC offset.

Request:

{
  "jsonrpc": "2.0",
  "method": "getTimeZone",
  "params": {},
  "id": 2
}

Response:

{
  "jsonrpc": "2.0",
  "result": {
    "timezone": "America/New_York",
    "offset": "-05:00"
  },
  "id": 2
}

3. getUnixTimestamp

Returns the current Unix timestamp in seconds.

Request:

{
  "jsonrpc": "2.0",
  "method": "getUnixTimestamp",
  "params": {},
  "id": 3
}

Response:

{
  "jsonrpc": "2.0",
  "result": {
    "timestamp": 1736509845
  },
  "id": 3
}

💻 Using the Frontend Client

The index.html file provides a user-friendly web interface to interact with the server.

Features

• Three Action Buttons: Send requests to each of the three available methods
• Live Response Display: Pretty-printed JSON responses
• Loading State: Visual feedback while waiting for responses
• Error Handling: Clear error messages if requests fail
• Clear Response: Button to clear the response area
• Last Request Timestamp: Shows when the last request was made
• Responsive Design: Works on desktop and mobile devices

How to Use

1. Start the server with npm start
2. Open index.html in your browser
3. Click "Get Current Time", "Get Time Zone", or "Get Unix Timestamp"
4. View the formatted JSON response
5. Use "Clear Response" to reset the display

🧪 Testing with cURL

Test getCurrentTime

curl -X POST http://localhost:3000/rpc \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","method":"getCurrentTime","params":{},"id":1}'

Test getTimeZone

curl -X POST http://localhost:3000/rpc \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","method":"getTimeZone","params":{},"id":2}'

Test getUnixTimestamp

curl -X POST http://localhost:3000/rpc \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","method":"getUnixTimestamp","params":{},"id":3}'

Test Health Check

curl http://localhost:3000/health

Test Server Info

curl http://localhost:3000/

📁 Project Structure

JSON-RPC-Protocol/
├── server.js              # Express server with JSON-RPC 2.0 implementation
├── index.html             # Frontend client (HTML + CSS + JavaScript)
├── package.json           # Project metadata and dependencies
├── package-lock.json      # Dependency lock file
├── README.md              # This file
├── .gitignore             # Git ignore rules
├── .gitattributes         # Git attributes
└── postman_collection.json # Postman API collection

🔐 CORS Support

The server includes CORS (Cross-Origin Resource Sharing) support, allowing the frontend client to communicate with the API from different origins. This is configured in server.js with the following headers:

• Access-Control-Allow-Origin: *
• Access-Control-Allow-Methods: GET, POST, OPTIONS
• Access-Control-Allow-Headers: Content-Type

🛠️ Development

Modifying the Server

To add new RPC methods:

1. Create a new function (e.g., function getNewMethod() { ... })
2. Add a case in the routeMethod() function
3. Document the method with JSDoc comments

Example: Adding a New Method

function getNewMethod() {
  return {
    data: 'your data here'
  };
}

// In routeMethod() switch statement:
case 'getNewMethod':
  return getNewMethod();

📦 Dependencies

• express (^4.18.2) - Web framework for Node.js

📄 License

ISC

🤝 Contributing

Feel free to modify and extend this project for your needs. This is a great learning resource for understanding JSON-RPC 2.0 implementation.

📞 Support

For issues or questions:

1. Check the README.md (this file)
2. Review the code comments in server.js and index.html
3. Test using the provided cURL examples or Postman collection
4. Verify the server is running on http://localhost:3000

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Created: January 11, 2026 Version: 1.0.0