IPWorks MQ 2020 ActiveX Edition

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Unsubscribe Method

Unsubscribes the control from one or more topic filters.

Syntax

mqttcontrol.Unsubscribe TopicFilter

Remarks

This method unsubscribes the control from one or more topic filters. The string passed for TopicFilter must contain one or more valid topic filter strings, separated by the delimiter string specified by the TopicDelimiter configuration setting (, by default).

The Unsubscribed event will fire when the server has acknowledged the unsubscribe request. However, note that the server's acknowledgment doesn't specify which topics a client was unsubscribed from. Please refer to the Unsubscribed event for more information.

To successfully unsubscribe from a topic filter, the exact filter must be passed to Unsubscribe, regardless of whether or not if contains wildcards. The server ignores any topic filters in an unsubscribe request which do not exactly match that of an existing subscription.

It is impossible to partially unsubscribe from a topic filter with wildcards (that is, if a client is subscribed to a topic filter home/floor1/+/#, requesting to unsubscribe from a topic filter home/floor1/livingRoom/temperature does nothing).

Similarly, because topic filters in an unsubscribe request are simply compared character-by-character with existing subscriptions rather than being interpreted, it is not possible to perform an action such as unsubscribing from all currently subscribed topics by passing "#" for TopicFilter.

Unsubscribe Example

// Unsubscribe from topic filters; have to use the exact same strings as before. If this
// was to be called after calling the code example shown for the Subscribe() method, we
// would still be subscribed to the "home" topic filter.
mqtt1.Unsubscribe("home/floor1/+/temperature,home/floor2/#");

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IPWorks MQ 2020 ActiveX Edition - Version 20.0 [Build 8162]