----------server-----------
#!/bin/bash
readonly iFIFO='/tmp/testfifo.in'
readonly oFIFO='/tmp/testfifo.out'
[[ -e "$iFIFO" ]] || mkfifo "$iFIFO"
[[ -e "$oFIFO" ]] || mkfifo "$oFIFO"
exec 3<"$iFIFO" 4>"$oFIFO"
while read; do
  if (( REPLY > 16384 )); then
    echo 'positive' >& 4
  else
    echo 'negative' >& 4
  fi
done <& 3
----------------------------

----------client------------
#!/bin/bash
readonly iFIFO='/tmp/testfifo.in'
readonly oFIFO='/tmp/testfifo.out'
[[ -r "$oFIFO" ]] || exit 255
[[ -w "$iFIFO" ]] || exit 255
exec 3>"$iFIFO" 4<"$oFIFO"
while sleep 1; do
  TEST="$RANDOM"
  echo "$TEST" >& 3
  read REPLY <& 4
  echo "$TEST: $REPLY"
done
----------------------------