ReadHandler

The ReadHandler interface is how the measurement data received from the outstation is passed to your application code. This callback interface is specified for each association you create and is invoked for both unsolicited responses and responses to polls.

When a response is parsed and determined to carry measurement data, ReadHandler callbacks are executed in the following order:

1. ReadHandler::beginFragment
2. ReadHandler::handle<TYPE> for each object header in the message
3. ReadHandler::endFragment

The begin/end methods provide useful information, including:

• The full header of the response
• Context regarding what triggered the response, such as unsolicited, startup integrity scan, periodic poll, etc.

tip

It's common to maintain a list of measurement values in your ReadHandler implementation. You can then use the endFragment method as a trigger to publish them. Since responses may consist of multiple fragments, you can inspect the ResponseHeader.Control.Fin field to determine if the current fragment is the final fragment in a response series.