Expose Localhost Services with Socat

Basic Usage

socat TCP-LISTEN:1880,fork TCP:127.0.0.1:1880

What This Does

• TCP-LISTEN:1880: Listen on port 1880 on all interfaces
• fork: Handle multiple connections simultaneously
• TCP:127.0.0.1:1880: Forward to localhost port 1880

Bind to Specific Interface

Only listen on a specific network interface:

socat TCP-LISTEN:1880,bind=192.168.1.100,fork TCP:127.0.0.1:1880

Common Use Cases

Expose Docker Container UI

# Container only listens on localhost:8080
socat TCP-LISTEN:8080,fork TCP:127.0.0.1:8080

Access Development Server

# Frontend dev server on localhost:3000
socat TCP-LISTEN:3000,fork TCP:127.0.0.1:3000

Proxy Database Connection

# PostgreSQL on localhost:5432
socat TCP-LISTEN:5432,fork TCP:127.0.0.1:5432

Run as Background Service

# Start in background
socat TCP-LISTEN:1880,fork TCP:127.0.0.1:1880 &

# Save the PID
echo $! > /tmp/socat.pid

# Stop later
kill $(cat /tmp/socat.pid)

Systemd Service

Create /etc/systemd/system/socat-proxy.service:

[Unit]
Description=Socat TCP Proxy
After=network.target

[Service]
Type=simple
ExecStart=/usr/bin/socat TCP-LISTEN:1880,fork TCP:127.0.0.1:1880
Restart=always

[Install]
WantedBy=multi-user.target

Enable and start:

sudo systemctl enable socat-proxy.service
sudo systemctl start socat-proxy.service

Security Warning

This exposes your service to your network. Consider:

• Using firewall rules to limit access
• Adding authentication
• Using SSH tunneling for sensitive services

Check Who’s Connected

sudo netstat -tnp | grep :1880