Simple Socket Server in Bash?
That is working as you expecting:
nc -k -l 4444 |bashand then you
echo "ls" >/dev/tcp/127.0.0.1/4444then you see the listing performed by bash.
[A Brief Security Warning]
Of course if you leave a thing like this running on your computer, you have a wide open gateway for all kinds of attacks because commands can be sent from any user account on any host in your network. This implements no security (authentication, identification) whatsoever and sends all transmitted commands unencrypted over the network, so it can very easily be abused.