Websocket Server in Bash [poc]

websocket_server.sh

#!/usr/bin/env bash

IN_PIPE=$1;


_hex() {
   typeset num=`echo 'obase=16; ibase=10; '"$1" | bc`
   if ((${#num} == 1)); then
      num=0"$num"
   fi
   printf "0x%s" $num
}

_send_frame() {
   typeset data="$1"
   typeset first_byte="0x81"
   typeset payload_length=${#data}
   typeset second_byte=`_hex $payload_length` # no mask
   
   printf "%s%s" $first_byte $second_byte | xxd -r -p
   printf "%s" "$data"
}

_connect() {
   rm -rf t
   while true
   do
      read packet
      echo $packet >> t
      cnt=`echo $packet | wc -c`
      if [ $cnt == 2 ] #end of message
      then
         key=`cat t | grep "Sec-WebSocket-Key:" | cut -f2 -d " "`
         keylen=`echo -n $key | wc -c`
         keylen=`expr $keylen - 1`
         key2=`echo -n $key | cut -c -$keylen`
         magic="258EAFA5-E914-47DA-95CA-C5AB0DC85B11"
         resp=`echo -n $key2$magic | openssl sha1 -binary | base64`
         echo   -ne "HTTP/1.1 101 Switching Protocols\r\n"
         echo   -ne "Connection: Upgrade\r\n"
         echo   -ne "Upgrade: websocket\r\n"
         echo   -ne "Sec-WebSocket-Accept: $resp\r\n\r\n"
         break
      fi
   done
   rm -rf t
}

# perform handshake
_connect;

# input loop
while true
do
   read input < $IN_PIPE;
   _send_frame "$input";
done