Shell – Howto create a permanent client connection with netcat

io-redirectionnetcatshell

I'm writing a bash script that constantly read a folder in a loop to send data to a server at a defined time interval. I'm using netcat as the tool to connect to the server and send the data. My pseudo code would look like:

while true
do
    read_folder()
    process_data() > result.txt
    cat result.txt > netcat ip port
    wait 10 sec
done

My only problem is that in the scenario the client connects and disconnects the TCP/IP connection to the server every time. I would prefer to establish the connection at the start of the script and close it at the end.

Is there any way this could be done with command line tools in a bash script?

Best Answer

Two separate processes: One that copies result.txt to netcat. Result.txt is fed via another process.

echo -n >result.txt
tail -f result.txt | nc ip port &
while true
do
    read_folder()
    process_data() > result.txt
    wait 10 sec
done

Related Solutions

How can a client talk to another client using unix domain sockets

So here is the thing, I guess I can respond to clients with:

echo "this is the response" | nc -lk -U /my/fifo

but the whole point is how do I respond differently depending on who the client is? I mean how can you create something very useful if there is no logic based on the client request etc?

My only guess is to have two servers:

nc -lk -U /my/fifo1 | while read line; do

  # custom logic goes here

done > nc -lk -U /my/fifo2

so then clients connect with:

echo '{"client_id":123}' | nc -U /my/fifo1 

nc -U /my/fifo2 | while read line; do

done;

this betrays what I know about how tcp and unix domain sockets work with Node.js etc, but I guess with bash we have to do it this way?

I also think to avoid race conditions might have to put the above two commands in a single pipe somehow.

Best Answer

Related Solutions

How can a client talk to another client using unix domain sockets

Related Question