get Transport Stats
Totals for the connection underneath this participant's media, as the server measures it: send.outgoingBitrate and receive.incomingBitrate in kbps, send.totalSentBytes and receive.totalReceivedBytes. A value the server did not report is null.
Asks the server and blocks the calling thread until it answers, so call it off the main thread.
Return
the stats, or null outside a room or when the request failed.