How do I change the "CONNECT_TIMEOUT_MILLIS" of minecraft server?

I am running a minecraft modded server. The version of server is 1.12.2.
I installed about 70 mods.
Somehow some of my client can not connect to my server.
It keep displaying “Connection timeout.”
Actually the delay between the server and client is less then 90ms.
I thought of a method which may fix this issue.
Change the “CONNECT_TIMEOUT_MILLIS” of minecraft server.
But I don’t know what to do.
Anybody help? I will appreciate that !:laughing: