Extended Network Connectivity (ENC) › ENC Gateway Connection Process

ENC Gateway Connection Process

The ENC Gateway functionality allows Client Automation to communicate with computers behind firewalls. If two computers want to connect but cannot normally do so because of a firewall in the way, the ENC Gateway arranges for them both to connect to a third computer that can relay data between the two computers.

In an ENC Gateway network, the connection process between two end points (computers) is as follows:

• End point 1 wishes to listen for connections on some port. Two ports are opened, one real and one virtual. The real port accepts direct connections; the virtual port is maintained by the ENC Client and listens for ENC Gateway connections.
• End point 2 wants to connect. The Socket Adapter tries to establish a direct connection. If this succeeds (it may be in the same network), the ENC Gateway has no further part to play.
• If it fails, the Socket Adapter asks the ENC Gateway Manager to arrange a connection.
• The ENC Gateway Manager sends a list of known ENC Gateway Routers to both end points. Each end point pings the routers and returns the results. The ENC Gateway Manager chooses a router that can be reached by both end points and tells each one to connect to it.
• Each end point connects to the ENC Gateway Router, which then relays data between them.

This relies on end points being able to connect outward bound from the firewalls around their networks to ENC Gateway Servers and ENC Gateway Routers. Inward bound connections are never made, so no inward bound ports need to be opened.