Does Gbridge software send back any information to Gbridge server?
Gbridge software will not send any of your personal information back to Gbridge server. It only needs to contact Gbridge NAT detection servers every time it starts to find out your current network environment. This would allow your friend to communicate with your computer directly when needed. During this process, Gbridge servers will know your network environment (e.g. public IP address, local IP address and NAT type), but not any other information (e.g. Google username/password, etc.). In some situations, it is impossible to establish direct connection between two computers, so the traffic has to be relayed by Gbridge relay servers. Because all traffic are encrypted, neither Gbridge nor Google has the key to decrypted them, so the communication is private and secure.
