The MG_ENABLE_BROADCAST macro indicates whether the mg_broadcast () function is enabled or not. What is the difference between enabling and disabling?

General
#1

The MG_ENABLE_BROADCAST macro indicates whether the mg_broadcast () function is enabled or not. What is the difference between enabling and disabling? Is it used for communication between the mongoose event manager and the active connection? The data of the active linked buffer is created by mg_socketpair Sent by the socket?
What does the code in the figure do?

#2

MG_ENABLE_BROADCAST enables mg_broadcast

See https://github.com/cesanta/mongoose/blob/6.16/mongoose.h#L4106-L4117