Alpine based Docker container with socat installed that can easily map multiple ports to another container
Changing the port mapping of an existing Docker container is not that easily done. After Googling around I found the suggestion
to use socat in a separate container which then will relay data transfers between the host and the target container.
Based on RobM's answer (see: Exposing a port on a live Docker container) I have
created an Alpine based Docker container with socat installed which expects the name of the target container and the port mapping to enforce.
Along with a nifty Bash script I have made it easy to set it all up.
Enter Portcat! :)
Run the following command:
curl -sL https://raw.githubusercontent.com/archan937/portcat/master/script/install | sudo bash
This script will install the executable portcat to /usr/local/bin/portcat.
As portcat is a command-line-tool, for starters you can print its help instructions:
PME-Legend ~> portcat -h
Usage:
portcat [OPTION] TARGET PORT [...PORT]
Options:
--daemon, [-d]
--help, [-h]
Run portcat container to proxy traffic
Pass both the name of the target container and the port mapping to enforce to portcat:
portcat my-awesome-container 3456 4444:8080
That's it! The executable will create a container called alpine-portcat which relays the data transfers :)
Please note that you can run portcat as a daemon with -d or --daemon.
The example above is equivalent to the following commands:
ipAddress=$(docker inspect my-awesome-container | grep IPAddress | grep -o '[0-9]\{1,3\}\(\.[0-9]\{1,3\}\)\{3\}' | head -n 1)
docker run -p 3456:3456 -p 4444:4444 --name=alpine-portcat -it pmelegend/portcat:latest $ipAddress 3456 4444:8080
You can detach using Ctrl+P followed by Ctrl+Q.
For support, remarks and requests, please mail me at pm_engel@icloud.com.
Copyright (c) 2021 Paul Engel, released under the MIT license
http://github.com/archan937 - http://twitter.com/archan937 - pm_engel@icloud.com
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
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