mjhjmtu

At the beginning, I created a small server with netcat and it worked well:

#!/bin/bash

PORT="1234";

startServer()
 fifo="fifo/$1";
 mkfifo "$fifo";

 connected="0";

 netcat -q 0 -l -p "$PORT" < "$fifo" 

mkdir fifo;
startServer 0;

It uses fifos to redirect the main loop output back to netcat.

Every call to startServer increases the value of $1 and creates a fifo file fifo/$1.

But I want to use bash's automatic file descriptor creation to get rid of fifo files and the parameter of startServer.

After multiple attempts, here is my current attempt at modifying the startServer function. I can receive lines from the client but unfortunately it does not receive anything back. I am confused about what is wrong.

startServer() while read -r line; do
 if [ "$connected" == "0" ];then
 #listen for a new connection
 startServer&
 connected="1";
 fi

 #server logic goes here

 done ) >&$fd;

 #close file descriptor
 exec fd<&-;
 exec fd>&-;

Also, I cannot use netcat's "-e" option since it is not available in the netcat-openbsd package.

You cannot set and use fd in the same command; you are effectively doing exec fd> ... >&$fd. What can work is creating the bash fifo/pipe first, using some simple command like :. Eg:

startServer()
 local connected=0 fd
 exec fd<> <(:)
 nc -q 0 -l -p "$PORT" <&$fd