Data forwarding through port and processing in the middle

netcat.sh

# so now we gonna forward data to different port but also process it in between
    # WARNING: if you working on mac replace default netcat with one from homebrew
        brew install netcat
    # for purpose of this tutorial lets assume that our machine ip address is: 192.168.180.74
    # first we need script to work as a middleware           
        # pipe.sh (remember about newline char \n instead of \r on \r\n - this is bash)
            BUFFER=""
            LASTNL="false"
            while read line; do
                if [ "$line" == "" ]; then
                    # echo 'nl'
                    if [ "$LASTNL" == "true" ]; then
                        # echo 'last true'
                        LASTNL="false"
                        echo -e $BUFFER | /bin/bash run.sh
                        BUFFER="";
                    else
                        # echo 'last false'
                        LASTNL="true"
                        BUFFER="$BUFFER\n"
                    fi
                else
                    # echo 'just data'
                    LASTNL="false"
                    BUFFER="$BUFFER\n$line"
                fi
                echo -e $line;
            done < "${1:-/dev/stdin}"
        # then we need script to process one chunk of data
            # run.sh (remember about newline char \n instead of \r on \r\n - this is bash)
                DATA=`cat`
                echo -e "\n::>${DATA}<::\n";
        # then setup pipe.sh script like
            nc -lp 45678 | /bin/bash pipe.sh | nc -lp 45679
        # in different console on the same machine run
            nc 192.168.180.74 45679
                # to listen on port 45678
        # and on another (third) console run:
            nc 192.168.180.74 45678
                # and here start writing something on the keyboard
                # from time to time press enter from one time to three time