A script to dump data from and to your service

mon.sh

#!/bin/bash

# Usage: ./my-service --listen=127.0.0.1:`mon 8080`

PORT=$(( ((RANDOM<<15)|RANDOM) % 63001 + 2000 ))

echo "$PORT"

socat -v TCP4-LISTEN:"$1",bind=127.0.0.1,reuseaddr,fork TCP4:"${2:-127.0.0.1}":$PORT >&2 & !

PID=$!

bash -c 'sleep 20; while nc -z '"${2:-127.0.0.1}"' '"$PORT"' ; do sleep 1; done; kill '"$PID" >&2 & !