callhome/callhome.sh

#!/bin/sh

USER=
HOST=

while true; do
  ssh -NC -o ServerAliveInterval=5 \
    -o UserKnownHostsFile=/dev/null \
    -o StrictHostKeyChecking=no \
    -R '<int IP>:50022:<rem IP>:22' \
    $USER@$HOST
  sleep 5
done