What's the idiomatic way of writing an Emacs front-end to a command which supports streaming input and output like Telnet?

Question

I would like to write an Emacs front-end to a server which supports Telnet connections, and I was wondering if there is an idiomatic way of doing this. Specifically, the program will work like this:

• Use the telnet function to connect to the server.
• Read the output of the telnet command so far, and transform it, and insert it into a buffer. This buffer will be different than the telnet buffer.
• Send commands to the telnet server as the user interactively executes functions

What I don't understand is the following:

• How can I programmatically read what the server is sending in the telnet process? Right now when I use the telnet function it creates a new buffer and switches to it, which is great for interactive use, but not for programmatic reading of output.
• The same for inputting something to the telnet process: how can I send text to it?

I know that a lot of Emacs packages use the command line to do things, but those commands are, as far as I know, pretty straightforward: you run the command, it gives you some output, and then quits. However, in this case the command keeps working in the background, and I need to read its output and send it input.

Thanks!

Answer 1

If the user doesn't interact directly with the process, then you're looking for start-(file-)process or make-process. Othrwise you might like to look at comint-exec.