Bash script for connection drain. Uses netstat to repeatedly count established connections

drain_port.sh

port=8080
max_tries=10
seconds_to_wait=3
echo "Waiting for traffic on port $port to stop..."
for (( tries=1; tries<=$max_tries; tries++ )); do
  # Netstat invocation tested on Ubuntu. Check your distro for differences.
  connections=$(netstat -ant | grep ":$port.*:.*ESTABLISHED" | wc -l)
  echo "  $connections connections remaining. Try $tries/$max_tries."
  if [ $connections -eq 0 ]; then
    exit 0
  fi
  sleep $seconds_to_wait
done
exit 1

example-run.out

Waiting for traffic on port 8080 to stop...
  8 connections remaining. Try 1/10.
  8 connections remaining. Try 2/10.
  7 connections remaining. Try 3/10.
  3 connections remaining. Try 4/10.
  0 connections remaining. Try 5/10.