Simple Socket Server in Bash?

Is there a way to quickly bind to a TCP port/ip address and simply print out all 开发者_运维知识库information to STDOUT? I have a simple debugging solution which writes things to 127.0.0.1:4444 and I'd like to be able to simply bind up a port from bash and print everything that comes across. Is there an easy way to do this?

$ nc -k -l 4444 > filename.out

see nc(1)

Just because you asked how to do it in bash, though netcat answer is very valid:

  $ exec 3<>/dev/tcp/127.0.0.1/4444
  $ cat <&3

That is working as you expecting:

 nc -k -l 4444 |bash

and then you

echo "ls" >/dev/tcp/127.0.0.1/4444

then 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.

Adding an answer using ncat that @Freedom_Ben alluded to:

ncat -k -l 127.0.0.1 4444

and explanation of options from man ncat:

-k, --keep-open            Accept multiple connections in listen mode
-l, --listen               Bind and listen for incoming connections