How to fix the flush method delay issue in the BufferedOutputStream android nougut?

I am developing one android application for server emulation(like Online terminal) using SocketChannel(Java Native) for stream connection. But in the application I am trying to flush the output stream every time after I send the data to the server. When I am doing that The flush method taking 2 to 4 seconds for it's execution in Nougat and above. And I tested that scenario with 5 different mobiles. Also in Marshmallow I tested the same scenario in 2 different mobiles that's work fine.?

Note:Now I am using BufferedOutputStream for writing data to the server.