typedef TReceivingDataEvent TReceivingDataEvent;
TReceivingDataEvent is the type of the OnReceivingData event of THTTPReqResp.
TReceivingDataEvent is the type of the OnReceivingData event handler, which is called after each chunk of data that is received when a large response has been broken into smaller chunks.
Read indicates the (cumulative) number of bytes that have been received.
Total indicates the total number of bytes that are expected.