CODEWITHSUNDEEP
linuxbashsocketstcp
Naftuli Kay
Naftuli Kay

Reputation: 91610

Simple Socket Server in Bash?

Is there a way to quickly bind to a TCP port/ip address and simply print out all 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?

Upvotes: 100

Views: 128762

Answers (4)

Kilokahn
Kilokahn

Reputation: 2311

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

Upvotes: 10

luk
luk

Reputation: 191

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.

Upvotes: 19

Diego Torres Milano
Diego Torres Milano

Reputation: 69188

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

Upvotes: 60

Nikolai Fetissov
Nikolai Fetissov

Reputation: 84151

$ nc -k -l 4444 > filename.out

see nc(1)

Upvotes: 137

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