A network system that includes a web application server on which a web application operates, one or more client terminals that access the web application server using a web browser, and printers that operate in conjunction with operation of the client terminal, and is configured so that at least the web application server and the client terminal, and the client terminal and a first printer of the printers, can respectively communicate over a network, the network system characterized by an interface board installed to the first printer receiving print data sent from the client terminal, wherein the printers include a second printer (3B, 3C) connected to a communication unit on the interface board, the interface board comprising: the communication unit having a plurality of communication ports to which the second printer (3B, 3C) and the client terminal are connected; a device information acquisition unit that finds a usable printer, and acquires device information including at least a printer ID for identifying the printer and connected communication port information from the found printer (3B, 3C); a device list generation unit that generates a device list based on the acquired device information, and a device list transmission unit that sends the generated device list to the client terminal; and the client terminal comprising: a web page acquisition unit (71; 314) that gets from the web application server a web page with an embedded print control script that operates on the web browser and controls printing related to a web page; a display unit that displays the acquired web page; a drawing process unit that accepts an inputting text and drawing figures on the displayed web page and draws a result of the inputted text and drawing figures in a canvas element; a print setting unit that prompts a user to input print settings including a paper size and number of copies; a print data generation unit that generates print data converting image data written in the canvas element to a form enabling processing by the printer according to the print control script when the user issues a print command on the displayed web page; a device list acquisition unit that acquires the device list from the interface board; a device selection unit that selects according to an input of the user one printer from the device list according to the print control script; and a print command unit (74; 214; 413; 525) that commands the printer selected by the device selection unit, via the interface board, to print the print data according to the print control script, wherein the interface board receives the print data from the client terminal and sends the print data to the printer selected by the device selection unit. the communication unit having a plurality of communication ports to which the second printer (3B, 3C) and the client terminal are connected; a device information acquisition unit that finds a usable printer, and acquires device information including at least a printer ID for identifying the printer and connected communication port information from the found printer (3B, 3C); a device list generation unit that generates a device list based on the acquired device information, and a device list transmission unit that sends the generated device list to the client terminal; a web page acquisition unit (71; 314) that gets from the web application server a web page with an embedded print control script that operates on the web browser and controls printing related to a web page; a display unit that displays the acquired web page; a drawing process unit that accepts an inputting text and drawing figures on the displayed web page and draws a result of the inputted text and drawing figures in a canvas element; a print setting unit that prompts a user to input print settings including a paper size and number of copies; a print data generation unit that generates print data converting image data written in the canvas element to a form enabling processing by the printer according to the print control script when the user issues a print command on the displayed web page; a device list acquisition unit that acquires the device list from the interface board; a device selection unit that selects according to an input of the user one printer from the device list according to the print control script; and a print command unit (74; 214; 413; 525) that commands the printer selected by the device selection unit, via the interface board, to print the print data according to the print control script, wherein the interface board receives the print data from the client terminal and sends the print data to the printer selected by the device selection unit.