Socat Proxy

A lightweight Docker container that creates a UNIX socket proxy to TCP connections using socat and Alpine Linux.

📑 Table of Contents

• 🚀 Features
• 📋 Use Case
• 🛠️ Configuration
  • Environment Variables
• 🚢 Quick Start
  • Using Docker Compose (Recommended)
  • Using Docker Run
• 🔧 How It Works
• 💡 Example: Secure Docker Socket Access for Host-Mode Containers

🚀 Features

• Configurable: Environment variable driven configuration
• Socket Management: Automatic UNIX socket creation and cleanup
• Production Ready: Includes proper error handling and logging

📋 Use Case

• Proxy Docker socket from a docker proxy to a container in host mode without directly exposing socket to host

🛠️ Configuration

Environment Variables

Variable	Default	Description	Example
TARGET_HOST	-	Target hostname/IP to proxy to	socket-proxy-beszel
TARGET_PORT	-	Target port to proxy to	2375
UNIX_SOCKET_NAME	-	Name of the socket file	docker.sock
UNIX_SOCKET_PATH	-	Path to UNIX socket inside container	/socket
HOST_SOCKET_PATH	-	Host path for socket mounting	/docker/beszel-agent/sock
DEBUG_LEVEL	-	Level of logs verbose	0,1,2,3

🚢 Quick Start

Using Docker Compose (Recommended)

1. Create a .env file with your configuration:

# .env
TARGET_HOST=socket-proxy-beszel
TARGET_PORT=2375
UNIX_SOCKET_NAME=docker.sock
UNIX_SOCKET_PATH=/socket
HOST_SOCKET_PATH=/docker/beszel-agent/sock
DEBUG_LEVEL=0

2. Create a compose.yml file:

services:
  socat-proxy:
    image: git.djeex.fr/djeex/socat-proxy:latest
    environment:
      - TARGET_HOST=${TARGET_HOST}
      - TARGET_PORT=${TARGET_PORT}
      - UNIX_SOCKET_NAME=${UNIX_SOCKET_NAME}
      - UNIX_SOCKET_PATH=${UNIX_SOCKET_PATH}
      - HOST_SOCKET_PATH=${HOST_SOCKET_PATH}
      - DEBUG_LEVEL=${DEBUG_LEVEL}
    volumes:
      - ${HOST_SOCKET_PATH}:${UNIX_SOCKET_PATH}
    restart: unless-stopped

3. Start the service:

docker compose up -d

Using Docker Run

docker run -d \
  --name socat-proxy \
  -e TARGET_HOST=socket-proxy-beszel \
  -e TARGET_PORT=2375 \
  -e UNIX_SOCKET_NAME=docker.sock \
  -e UNIX_SOCKET_PATH=/socket \
  -e HOST_SOCKET_PATH=/docker/beszel-agent/sock \
  -e DEBUG_LEVEL=1 \
  -v /docker/beszel-agent/sock:/socket \
  git.djeex.fr/djeex/socat-proxy:latest

🔧 How It Works

1. Socket Check: Verifies if UNIX socket exists at startup
2. Cleanup: Removes existing socket file/folder if present
3. Socket Creation: Creates new UNIX socket using nc -lU
4. Proxy Start: Starts socat to proxy UNIX socket to TCP endpoint

💡 Example: Secure Docker Socket Access for Host-Mode Containers

Beszel is a monitoring tool that requires network_mode: host to function properly. This creates a security challenge: Beszel needs access to the Docker socket, but it cannot reach a containerized docker-socket-proxy due to the network isolation. Running docker-socket-proxy in host mode would be highly insecure.

Socat-proxy solves this problem by creating a secure bridge between host-mode containers and containerized socket proxies. It exposes a UNIX socket file on the host filesystem that Beszel can access, while securely forwarding all Docker API requests to the socket-proxy running on the bridge network.

services:
  socat-proxy:
    image: git.djeex.fr/djeex/socat-proxy:latest
    container_name: socat-proxy-beszel
    environment:
      - TARGET_HOST=${TARGET_HOST}
      - TARGET_PORT=${TARGET_PORT}
      - UNIX_SOCKET_PATH=${UNIX_SOCKET_PATH}
      - HOST_SOCKET_PATH=${HOST_SOCKET_PATH}
      - UNIX_SOCKET_NAME=${UNIX_SOCKET_NAME}
    volumes:
      - ${HOST_SOCKET_PATH}:${UNIX_SOCKET_PATH}
    restart: unless-stopped

  socket-proxy:
    image: lscr.io/linuxserver/socket-proxy:latest
    container_name: socket-proxy-beszel
    security_opt:
      - no-new-privileges:true
    environment:
      - CONTAINERS=1
      - INFO=1
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock:ro
    restart: unless-stopped
    read_only: true
    tmpfs:
      - /run

  beszel-agent:
    image: henrygd/beszel-agent:latest
    container_name: beszel-agent
    restart: unless-stopped
    network_mode: host
    security_opt:
      - no-new-privileges:true
    volumes:
      - ${HOST_SOCKET_PATH}/docker.sock:/var/run/docker.sock:ro
    environment:
      - #... your Beszel environment var 
    depends_on:
      - socat-proxy