Adding a New Port to an Existing Docker Container

Overview

This guide explains how to add a new port to an existing Docker container using alpine/socat and Docker networking.

Steps

1. Create a Docker Network

   First, create a Docker network to connect your containers.

    docker network create my-network
   

2. Connect the Existing Container to the Network

   Connect your existing container to the newly created network.

    docker network connect my-network my-container
   

3. Run alpine/socat to Forward the Port

   Run a new Docker container using the alpine/socat image to forward the desired port to the existing container. This example forwards port 1883.

    docker run -d --name rabbitmq-mqtt-proxy --network my-network -p 1883:1883 alpine/socat tcp-listen:1883,fork,reuseaddr tcp-connect:my-container:1883
   

   • -d: Run the container in detached mode.
   • --name rabbitmq-mqtt-proxy: Name the new container rabbitmq-mqtt-proxy.
   • --network my-network: Connect the new container to my-network.
   • -p 1883:1883: Map port 1883 on the host to port 1883 in the container.
   • alpine/socat: Use the alpine/socat image.
   • tcp-listen:1883,fork,reuseaddr: Listen on port 1883 and forward connections.
   • tcp-connect:my-container:1883: Connect to port 1883 on the existing container named my-container.

Summary

By following these steps, you can forward a new port to an existing Docker container using alpine/socat and Docker networking. This allows you to expose additional services without modifying the original container configuration.