In forwarding a port range is redirected, in port triggering a given single port is redirected.
You want to forward a single port in a forwarding port - not this tab - you do it in port triggering.
Please also remember that Horizon is something like a modemorouter - here the port is unblocked on Horizon and not a given computer.
It remains to enter the IP of the computer in the DMZ Host tab - people who have their modem routers: Thomson, Cisco or Technicolor have similar - here and there the external IP has a modem router, not a computer in the network and the redirection does not work.
It remains to replace Horizon with a regular cable modem by changing it from modemorouter to bridge (it should have such an option) - but this requires buying your own router, if we have more than one computer on the local network - only one computer works in a bridg without its own router.
