>>So how does your connectionstring look like, you use localhost or server IP? Normally I would expect the MySql engine to be installed only on the server, where the data folder is.
>>
>>>>But that would mean that MySql is running on your local computer, and not on a server. Is this a test environment or you did that in the production environment?
>>>
>
>This is a production environment.
>I installed MySQL engine on every PCs, while the database is on the server only.
>
>I have tried install MySQL engine on server only, but it runs very slow.
>This is LAN environment, not online, not using internet.
>

To run on the server, with multiple connections, try in Mysql settings to add the following:

# To avoid slow connection because of a reverse DNS lookup:
skip-name-resolve