IT FINALY WORKS!!!
With Carrara 8, Windows 7, on all machines
This is what I did to make my nodes see by my host application:
- Make sure both the main application and the render nodes are same version (latest)
- 4 advanced definitions in windows firewall, on host and slave machines: Open ports 5020-5080 in TCP and UPD, entering and outgoing,
- Open the ports 5020-5080 on my rooter (Forwarding/virtual server, on my TP-Link)
- Disable my anti-virus, it had a firewall of its own
So with all this, IT WORKS