UpdateWillTopic Method
Update the will topic, will QoS and will retain flag stored in session state data by the server.
Syntax
mqttsn.updateWillTopic([callback])
Callback
The 'callback' parameter specifies a function which will be called when the operation completes (or an error is encountered). If the 'callback' parameter is not specified, then the method will block and will not return until the operation completes (or an error is encountered).
The callback for this method is defined as:
function(err){ }
'err' is the error that occurred. If there was no error, then 'err' is 'null'.
'err' has 2 properties which hold detailed information:
err.code err.message
Remarks
When this message is called, the value of WillTopic, WillQOS and WillRetain will be used to update the will message stored by the server.
This method may be called when these values are empty, in this case the server values will be cleared.
See UpdateWillMessage for more on updating will settings.