ClientId Property

A string that uniquely identifies this instance of the class to the server.

Syntax

 mqtt.getClientId([callback])
 mqtt.setClientId( clientId, [callback])

Default Value

""

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 the getClientId([callback]) method is defined as:

function(err, data){ }

'err' is the error that occurred. If there was no error, then 'err' is 'null'.

'data' is the value returned by the method.

The callback for the setClientId([callback]) 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

The ClientId string is used by the server to uniquely identify each client that is connected to it. In MQTT 5, when the SessionExpInterval config is set to a positive value, the server will also associate it with any session state data that needs to be saved for the length of time specified when the class is disconnected.

If ClientId is empty when Connect is called, the class's behavior depends on value of CleanSession. If CleanSession is True, the class will automatically generate a unique value for ClientId before connecting. If CleanSession is False, the class fails with an error.

This property is not available at design time.

Data Type

String