Fired while a document transfers (delivers document).
The 'callback' is called when the 'Transfer' event is emited.
The argument 'e' has the following properties:
e.direction e.bytesTransferred e.percentDone e.text (buffer)
The Text parameter contains the portion of the document text being received. It is empty if data is being posted to the server.
The BytesTransferred parameter contains the number of bytes transferred in this Direction since the beginning of the document text (excluding HTTP response headers).
The Direction parameter shows whether the client (0) or the server (1) is sending the data.
The PercentDone parameter shows the progress of the transfer in the corresponding direction. If PercentDone can not be calculated the value will be -1.
Note that events are not re-entrant. Performing time consuming operations within this event will prevent it from firing again in a timely manner and may impact overall performance.