SSH Forwarder

A dynamic SSH forwarding system that automatically updates SSH port forwarding when the client's IP address changes.

Overview

This system consists of two components:

• Client (client.js): Monitors public IP changes and notifies the server
• Server (server.js): Receives IP updates and maintains SSH port forwarding

Setup

1. Install Dependencies

npm install

2. Configure Environment

Edit the .env file with your settings:

# Server configuration (for client to connect to)
SERVER_HOST=your-server-ip-here
SERVER_PORT=3000

# SSH forwarding configuration
SSH_FORWARD_PORT=2222
SSH_TARGET_PORT=22

# Client configuration
CHECK_INTERVAL=30000

Configuration Details:

• SERVER_HOST: IP address of the server where server.js runs
• SERVER_PORT: Port for the HTTP API (default: 3000)
• SSH_FORWARD_PORT: Port on server that will forward SSH connections (default: 2222)
• SSH_TARGET_PORT: SSH port on the client machine (default: 22)
• CHECK_INTERVAL: How often to check for IP changes in milliseconds (default: 30 seconds)

3. Deployment

On the Server Machine:

1. Copy the project files to your server
2. Configure the .env file
3. Run: npm run server or node server.js

On the Client Machine:

1. Copy the project files to your client machine
2. Configure the .env file with your server's IP
3. Run: npm run client or node client.js

Usage

Starting the Server

npm run server

The server will:

• Start an HTTP API on the configured port
• Wait for IP updates from clients
• Create SSH forwarding when a client IP is received

Starting the Client

npm run client

The client will:

• Check its public IP address immediately
• Monitor for IP changes at regular intervals
• Notify the server when IP changes are detected

Connecting via SSH

Once the client has reported its IP to the server, you can SSH through the server:

ssh -p 2222 username@your-server-ip

This will forward your connection to the client machine's SSH port.

API Endpoints

The server provides several endpoints:

• GET /health - Health check and current status
• POST /update-ip - Endpoint for clients to report IP changes
• GET /status - Detailed forwarding status

Features

• Automatic IP Detection: Uses public IP detection to handle NAT/firewall scenarios
• Dynamic Forwarding: Automatically updates SSH forwarding when client IP changes
• Graceful Handling: Properly closes old connections before establishing new ones
• Monitoring: Built-in health checks and status endpoints
• Error Recovery: Robust error handling and connection management

Security Considerations

1. Firewall: Ensure the server's SSH forward port is accessible
2. Authentication: SSH authentication is handled by the target machine
3. Network: Consider using HTTPS for the client-server communication in production
4. Access Control: Implement additional authentication for the API endpoints if needed

Troubleshooting

Client Issues

• Check if SERVER_HOST and SERVER_PORT are correct
• Verify network connectivity to the server
• Check for firewall restrictions

Server Issues

• Ensure the SSH forward port is not in use by another service
• Check firewall rules for both the API port and SSH forward port
• Verify the client machine's SSH service is running and accessible

Connection Issues

• Test direct SSH connection to verify credentials
• Check if the client's IP is correctly reported to the server
• Verify port forwarding is active using the /status endpoint