Why did you did this?

I wanted to do something with sockets in node. Also this shows how easy is for an attacker to do something dangerous. Anyone can do it, we have to be very careful with untrusted code

Why specify the host and port as environment variables instead of as program arguments?

Just because I think the code is cleaner this way, I didn't want unnecessary complexity

Server: run an interactively server, it waits for a connection and then allows the user to send commands to the client

    PORT='<Port where the server will listen to connections>' npm run server

Node REPL client: connects to the server and silently provides the server access to a Node REPL in the client machine

    # In the machine with the role of the client
    HOST='<Server IP>' PORT='<Server port>' npm run client:node

Shell client: connects to the server and silently provides the server execution of shell commands in the client machine

    # In the machine with the role of the client
    HOST='<Server IP>' PORT='<Server port>' npm run client:shell

First run the server with

    PORT='8080' npm run server

Then run the client on another terminal tab with

    HOST='localhost' PORT='8080' npm run client:node

Now go back to the terminal with the server process and you can interact with the client Node REPL.

    > process.arch
    'x64'
    > 2 + 3
    5
    > process.stdout.write('Hello') // Outputs "Hello" in the client process
    true

To stop the server you can send a kill signal with Ctrl+C