Dear admin,
i wanna ask about polling time, what is it?
and where i can see in interface freichat different between comet and short polling thanks

there is no difference in the interface.
the client(FreiChat) repeatedly checks the database for new chat messages. the lower the time interval between two subsequent checks(or requests) the more real time the chat is.

but lowering the poll interval has a cost as it will put more load on the server.

Now there are two ways of polling , short poll and comet.

in short poll, you request the server after the SET time interval. Here memory is allocated and freed for every request. but the repeated requests may put load on the server.

but in comet, once requested, you don't disconnect from the server for a period of 30 seconds. this also means the server should have the capacity to allocate memory and CPU to all the logged in users.

You can read more on these topics by searching on Google.