poco Socket::select() APi not waiting for a file descriptor to become ready for gievn Poco::Timespan

I am using POCO library for socket connection.

I Notice poco select API doesn't wait till the poco::timespan.

 ReadData() {
  SocketList read;
  SocketList write;
  Socket::select(read, write, exception, Poco::Timespan(5,0)); // it doesn't wait for 5 sec? 
  Extract_data(read);
}