Patent ID: 7577746

Claim:
A network system, comprising: a client terminal that requests a peer-to-peer communication; and a host terminal that supports a connection of the peer-to-peer communication, wherein said client terminal generates a request message embodied by an electronic mail message that contains in the message body at least one character indicating an IP address of said client terminal, and said client terminal sends out the request message to said host terminal via a transmission mail server, wherein said host terminal acquires the request message via a reception mail server, said host terminal extracts the IP address of said client terminal from a description content of the message body of the request message, said host terminal stores the extracted IP address in a table, said host terminal selects at least one IP address from the table and generates a reply message embodied by an electronic mail message containing in the message body at least one character indicating the selected at least one IP address, and said host terminal sends the reply message to said client terminal via the transmission mail server, and wherein said client terminal acquires the reply message via the reception mail server, said client terminal extracts at least one IP address of other terminals from a description content the message body of the reply message, and said client terminal starts a peer-to-peer communication of data transmission and reception with another terminal which is specified based on the extracted IP address.