Reliable methods of creating SSH tunnels for TCP forwarding

ssh-tunnel.sh

#Source: https://stackoverflow.com/questions/2241063/bash-script-to-setup-a-temporary-ssh-tunnel

#SSH feature - control sockets 
ssh -4 -o StrictHostKeyChecking=no -i ~/.ssh/id_rsa -M -S my-ctrl-socket -fnNT -L 10023:remoteserver.com:8000 dev@middleserver.internal

#Get PID - you'll have to parse this
ssh -S my-ctrl-socket -O check dev@middleserver.internal

#Exit
ssh -S my-ctrl-socket -O exit dev@middleserver.internal

#-------------
# Another way without control sockets

ssh -4 -o StrictHostKeyChecking=no -i ~/.ssh/id_rsa -Cfo ExitOnForwardFailure=yes  -NL 10023:remoteserver.com:8000 dev@middleserver.internal
PID=$(pgrep -f 'NL 10023')
[ "$PID" ] || exit 1