A network system has a firewall that connects an external network and an internal network. A terminal device is provided on the external network. An application server is provided on the internal network and provides data to the terminal device based on a request from the terminal device. An external server is provided on a DMZ of the firewall or on the external network, and relays communication between the terminal device and the application server based on the request from the terminal device through an internal server. The internal server is provided on the internal network, and relays communication between the external server and the application server. The internal server has an encrypting unit that encrypts the packet in such a manner that an encrypted packet is able to be decrypted only by the terminal device.