Netcat Socket Programming

Question

I am facing some issues to solve a problem. A server program is giving 4 random unsigned integer numbers everytime I connect to it. My job is to add the 4 numbers and send back the sum. But the time is restricted. So if I want to use a calculator to do the job, it is not possible. Thus I have to take resort to scripting. I want to connect to the the server using netcat, retrieve the 16 bytes, pipe the data to my C program(which will parse the data into 4 unsigned int variables and print out the sum) and again redirect this program output to netcat

netcat <server> <port> | myProg | netcat <server> <port>

But the tcp socket netcat is opening second time is not the previous socket. So a different set of 4 numbers would be presented this time, which defeats the entire effort. My question is: Is it possible by any means(using netcat) to use the previous socket (opened by netcat) to pump the calculated sum back to the server?

I dont want to use C to do socket programming as it is very tough for me. Also I know

echo 3<>/dev/tcp/server/port
cat <&3 | ./myprog | more >&3

probably will solve my purpose (correct me if I am wrong). But I would like to do it the netcat way. Thanks in advance.

Answer 1

Use socat instead of netcat.

socat can spawn the command itself, with input and output both redirected (you don't use shell redirection, let socat handle it)

socat TCP:server,port SYSTEM:myProg