| CPC G05B 19/042 (2013.01) [G05B 2219/24215 (2013.01)] | 4 Claims |

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3. An HMI client, wherein
the HMI client displays an HMI screen on a web browser, a display part related to a monitoring target being arranged on the HMI screen, receives signal data, a unique identifier and a signal value being associated with each other in the signal data, the unique identifier specifying the display part, the signal value being related to the monitoring target, and changes a display content of the display part corresponding to the received signal data; and
the HMI client comprises:
a memory that stores a program and temporarily stores the signal data in a buffer area;
a processor that is configured to make a communication thread and a DOM update thread run in parallel on the web browser by executing the program; and
a display that displays the web browser;
the communication thread executes:
reception processing of periodically receiving the signal data from the web HMI server;
buffer overwrite processing of overwriting signal data stored in the buffer area with the received signal data when a unique identifier included in the received signal data and a unique identifier included in the signal data stored in the buffer area are the same; and
buffer transmission processing of transmitting a DOM update request event to the DOM update thread when receiving a signal data request event from the DOM update thread, the DOM update request event including all signal data stored in the buffer area; and
the DOM update thread executes:
DOM update processing of updating a DOM for all the signal data included in the DOM update request event when receiving the DOM update request event; and
after updating the DOM, rendering processing of transmitting the signal data request event to the communication thread and updating, according to the updated DOM, a display content of the display part displayed on the web browser.
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