Replacement for UDP. Instead of sending packets via UDP, a TCP connection is opened to a Router (using the RouterStub client-side stub), the IP address/port of which was given using channel properties
router_host and
router_port. All outgoing traffic is sent via this TCP socket to the Router which distributes it to all connected TUNNELs in this group. Incoming traffic received from Router will simply be passed up the stack.
A TUNNEL layer can be used to penetrate a firewall, most firewalls allow creating TCP connections to the outside world, however, they do not permit outside hosts to initiate a TCP connection to a host inside the firewall. Therefore, the connection created by the inside host is reused by Router to send traffic from an outside host to a host inside the firewall.
@author Bela Ban