Connected Property

Triggers a connection or disconnection.

Syntax

property Connected: Boolean read get_Connected write set_Connected;

Default Value

false

Remarks

This property triggers a connection or disconnection. Setting this property to True makes the component attempt to connect to the host identified by the RemoteHost property. If successful, after the connection is achieved the value of the property changes to True and the Connected event is fired.

Setting this property to False closes the connection.

By default the component will connect in plaintext. To enable SSL set SSLEnabled to True.

In addition, WebSocket connections are supported. To connect using WebSockets specify a hostname beginning with ws:// (plaintext) or wss:// (SSL). For instance, ws://test.mosquitto.org.

When connecting to an MQTT server, the component sends the following information:

• The values of the ClientId, CleanSession, and KeepAliveInterval properties.
• The value of the User property (if non-empty).
• The value of the Password property (if non-empty).
• The values of the WillTopic and WillMessage properties and the WillQOS and WillRetain configuration settings.
• MQTT 5 specific values from ClientTopicAliasMax, SessionExpInterval, ConnectProperties and WillProperties.

If CleanSession is True, check the SessionPresent configuration setting once connected to determine whether the server actually had any session state saved.

Refer to CleanSession, SaveSession, and RestoreSession for more information about MQTT sessions and session state persistence; refer to WillTopic, WillMessage, WillQOS, and WillRetain for more information about MQTT Wills.

Basic Connection Example

This property is not available at design time.