exec 3<>/dev/tcp/hostname/port
echo "request" 1>&3
response="$(cat <&3)"

$ nc -l localhost 3000

$ nc localhost 3000

#!/bin/bash

coproc netcat -l localhost 3000

while read -r cmd; do
  case "$cmd" in
    d) date ;;
    q) kill "$COPROC_PID"
       exit ;;
    *) echo "What?" ;;
  esac
done <&${COPROC[0]} >&${COPROC[1]}

q

echo GET / HTTP/1.0 | nc 0 80
HTTP/1.1 400 Bad Request
Date: Thu, 12 Jan 2017 13:44:23 GMT
Server: Apache/2.4.18 (Ubuntu)
Content-Length: 311
Connection: close
Content-Type: text/html; charset=iso-8859-1