Patent ID: 7707628

Claim:
A network system, comprising: a firewall that connects an external network and an internal network; a terminal device being provided on the external network; an application server being provided on the internal network, the application server that provides data to the terminal device based on a request from the terminal device; and an external server being provided on a DMZ of the firewall or on the external network, the external server configured to receive a request from the terminal device to connect to the application server and relay communication between the terminal device and the application server through an internal server; the internal server being provided on the internal network, the internal configured to relay communication between the external server and the application server, the internal server further, comprising: a receiving unit that receives a packet for the terminal device from the application server; 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; and a transmitting unit that transmits the encrypted packet to the external server via the firewall, the external server further comprising: a receiving unit that receives the packet encrypted by the internal server; and a transmitting unit that transmits the received encrypted packet to the terminal device, wherein decryption of the received encrypted packet is suppressed in the external server by changing an absolute address information for accessing a communication device, communication between the external server and the internal server is permitted when a session is established based on a connection request from the internal server to connect to the external server, and the external server relays the request from the terminal device for connection to the application server through the internal server as a response to the connection request from the internal server, wherein the internal server or the terminal device further comprises: a determining unit that determines whether or not the packet received by the receiving unit contains the absolute address information for accessing the communication device, the communication device including the application server or a database server connected to the internal network, the database server providing additional information to the terminal device, and a changing unit that changes the absolute address information to address information via the external server when absolute address information is contained in the packet received by the receiving unit.