Build a ssh tunnel in the background and test the port every 30 seconds if tunnel gone away build again.

build_ssh_tunnel.sh

#!/bin/bash

while true ; do
    listen=`netstat -f inet -p tcp -nRa | grep 'LISTEN' | awk '{ print $4 }' | grep 18080`
    if [ -z $listen ]; then
        nohup ssh -ntt -D 18080 user@domain.com > /dev/null 2>&1 &
    fi
    sleep 30
done