tcp-proxy

README

tcp-proxy

A simple, dependency-free proxy for TCP connections.

What is this exactly and how does it work?

Well, a (reverse) proxy for TCP connections. It listens for incoming TCP connections (by default on port 3110) and forwards them to the particular server (by default on 0.0.0.0:22). IP and port of the server can be passed via command line arguments or by sending the new it dynamically to a listener (which is by default listening on 0.0.0.0:3111).

So, what can this be used for?

The idea is that a reverse proxy like this is set up on a machine with a static IP so that it proxies a machine with dynamic IP. The machine with dynamic IP would send its IP to the server when it detects it has changed. This makes possible for the client to connect to the machine with dynamic IP without needing to know its IP at all.

|--------|         |---------------|         |----------------|
| Client | ------> | Reverse Proxy | ------> | Remote Machine |
|        | <------ |  (static IP)  | <------ |  (dynamic IP)  |
|--------|         |---------------|         |----------------|  

How you use it it's completely up to you. I needed a way to ssh into my machine with a dynamic IP and I didn't like services like ngrok (that's why the default port of the remote machine is 22). Your use case may be same or entirely different.

How can I run this?

To run this, you'll need the Go tool installed (through golang.org or your favorite package manager via package go). This project utilizes go modules so Go 1.12+ is required, preferably Go 1.15+.
To install this tool you can run go install, this way you can use it anywhere on the system via command tcp-proxy. Installing this it is not required, it is possible to run it using go run . in the source code directory.

Running this tool without passing any arguments will use these default settings:

• the listener for client connections will listen on 0.0.0.0:3110. By default, it is possible to maintain 16 concurrent connections (this can be changed using command line arguments)
• the listener for address updates will listen on 0.0.0.0:3111
• on client connection, the proxy will forward the connection to 0.0.0.0:22. Dynamic IP updates will change the remote IP if the passed IP is valid. The port cannot be changed during runtime.
  To change these settings, command line arguments should be passed like this:

tcp-proxy -clientListener="192.168.1.10:80" -addrUpdateListener="0.0.0.0:3000" -initialRemoteAddr="192.168.1.18:22" -maxConns=10

or with go run:

go run . -clientListener="192.168.1.10:80" -addrUpdateListener="0.0.0.0:3000" -initialRemoteAddr="192.168.1.18:22" -maxConns=10

This will create a listener for client connection on 192.168.1.10 on port 80, a listener for remote machine IP updates on 0.0.0.0 (all intefaces) on port 3000 and it will set as 192.168.1.18 the initial address of the remote machine and port 22 as the permanent port of the remote machine.

Final Thoughts

Everything is subject to change mostly according to my own needs, that means that plans of releasing 1.0 are nowhere near. Nevertheless, I'm open to any feedback to improve this piece of software to fit needs not just myself, but others as well (: