Redirect process stdin and stdout to netcat

Question

I have an embedded linux application with a simple interactive command line interface.

I\'d like to access the command line from telnet (or network, in general).

Answer 1

I found that by using bash v. >= 4.0 I can use coproc:

#!/bin/bash

coproc myapp
nc -kl -p 4000 <&"${COPROC[0]}" >&"${COPROC[1]}"

EDIT

I eventually incorporated a telnet server in my cli library. You can find the result on GitHub: https://github.com/daniele77/cli

Answer 2

You can use ncat (from nmap package: apt install nmap) for that as well as follow:

ncat -lnvp 443 -e myapp

don't forget to fflush(stdout); after each printf("%s",str); in your app

Answer 3

Is there a way to redirect both stdin and stdout to netcat

There is socat, which is a more advanced netcat. You can redirect both stdin and stdout with it. E.g.:

socat TCP4-LISTEN:5556,reuseaddr,fork EXEC:"cat - /etc/redhat-release"

In the above cat reads stdin and /etc/redhat-release and outputs them into stdout.

And then try using that:

$ echo "hello" | nc 127.0.0.1 5556
hello
Fedora release 22 (Twenty Two)

$ echo "hello 2" | nc 127.0.0.1 5556
hello 2
Fedora release 22 (Twenty Two)