Send a request cancellation message to tell the server to cancel processing request in this connection.
<br>Note: Use this with caution because the cancellation signal may or may not have any effect.
@param handler the handler notified if cancelling request is sent
@return a reference to this, so the API can be used fluently
Send a request cancellation message to tell the server to cancel processing request in this connection. <br>Note: Use this with caution because the cancellation signal may or may not have any effect.
@param handler the handler notified if cancelling request is sent @return a reference to this, so the API can be used fluently