Abstract: To provide a new network system, a new network connection device and a new reverse proxy device enabling to solve the problems of the conventional VPN and achieve strong security and flexible operability by adding extremely light software and hardware. After a static NAT forming device has performed authentication with a conductor through a control session, if a terminal makes a connection request to a server in a network existing before a reverse proxy server, the static NAT forming device and a stepping node will set a static NAT, and the reverse proxy server will set a reverse proxy, so that a data session will be formed between the terminal and the server. By configuring a network system in such a manner, it is possible to pass through the firewall to achieve a connection from the terminal to the server in a virtual connection state without causing private address collision.