A network system comprising: at least one terminal device; a control device configured to control a machine; and a server device configured to receive data including at least one of image data and audio data from at least one of the control device and the terminal device that are connected via a network, and to distribute the received data to a different device from the device that transmitted the data, wherein the control device includes: a controller configured to execute a control operation; a communication unit configured to transmit data indicating an operational state of the machine that is controlled to the server device; and a storage configured to store setting information associating attribute information with input/output information collected from the machine that is controlled, characterized in that the terminal device includes a display unit configured to display the operational state of the machine controlled by the control device together with a state of another terminal device connected to the server device, and the control device is configured to perform a search as to whether attribute information corresponding to text included in a message distributed from the server device exists, and, when attribute information corresponding to the text is retrieved, to transmit input/output information corresponding to the retrieved attribute information to the server device, to search an additional information defined in a variable management information held by the control device using a keyword that is included in the message distributed from the server and to determine whether the additional information is matching the keyword, and to transmit a message including the variable name and value corresponding to the additional information matching the keyword to the server device. at least one terminal device; a control device configured to control a machine; and a server device configured to receive data including at least one of image data and audio data from at least one of the control device and the terminal device that are connected via a network, and to distribute the received data to a different device from the device that transmitted the data, wherein the control device includes: a controller configured to execute a control operation; a communication unit configured to transmit data indicating an operational state of the machine that is controlled to the server device; and a storage configured to store setting information associating attribute information with input/output information collected from the machine that is controlled, characterized in that the terminal device includes a display unit configured to display the operational state of the machine controlled by the control device together with a state of another terminal device connected to the server device, and the control device is configured to perform a search as to whether attribute information corresponding to text included in a message distributed from the server device exists, and, when attribute information corresponding to the text is retrieved, to transmit input/output information corresponding to the retrieved attribute information to the server device, to search an additional information defined in a variable management information held by the control device using a keyword that is included in the message distributed from the server and to determine whether the additional information is matching the keyword, and to transmit a message including the variable name and value corresponding to the additional information matching the keyword to the server device. a controller configured to execute a control operation; a communication unit configured to transmit data indicating an operational state of the machine that is controlled to the server device; and a storage configured to store setting information associating attribute information with input/output information collected from the machine that is controlled, characterized in that the terminal device includes a display unit configured to display the operational state of the machine controlled by the control device together with a state of another terminal device connected to the server device, and the control device is configured to perform a search as to whether attribute information corresponding to text included in a message distributed from the server device exists, and, when attribute information corresponding to the text is retrieved, to transmit input/output information corresponding to the retrieved attribute information to the server device, to search an additional information defined in a variable management information held by the control device using a keyword that is included in the message distributed from the server and to determine whether the additional information is matching the keyword, and to transmit a message including the variable name and value corresponding to the additional information matching the keyword to the server device. to perform a search as to whether attribute information corresponding to text included in a message distributed from the server device exists, and, when attribute information corresponding to the text is retrieved, to transmit input/output information corresponding to the retrieved attribute information to the server device, to search an additional information defined in a variable management information held by the control device using a keyword that is included in the message distributed from the server and to determine whether the additional information is matching the keyword, and to transmit a message including the variable name and value corresponding to the additional information matching the keyword to the server device.