Unsubscribed Event

Fires when the server has acknowledged an unsubscribe request.

Syntax

public event OnUnsubscribedHandler OnUnsubscribed;

public delegate void OnUnsubscribedHandler(object sender, MqttUnsubscribedEventArgs e);

public class MqttUnsubscribedEventArgs : EventArgs {
  public string TopicFilters { get; }
  public int ResponseCode { get; }
}
Public Event OnUnsubscribed As OnUnsubscribedHandler

Public Delegate Sub OnUnsubscribedHandler(sender As Object, e As MqttUnsubscribedEventArgs)

Public Class MqttUnsubscribedEventArgs Inherits EventArgs
  Public ReadOnly Property TopicFilters As String
  Public ReadOnly Property ResponseCode As Integer
End Class

Remarks

This event fires when the server has acknowledged an unsubscribe request sent with Unsubscribe (that is, unlike the Subscribed event, this event fires only once for each call to Unsubscribe, regardless of how many topic filters are passed to it).

Note that in MQTT 3.1.1, servers do not specify which topic filters a client has been successfully unsubscribed in their acknowledgments. In fact, they will still acknowledge an unsubscribe request even if none of the topic filters included matched existing subscriptions. It is up to the client to keep track of what topics it is subscribed to; the TopicFilters parameter is provided as a convenience, its value simply a copy of the value passed to Unsubscribe originally.

Possible values for ResponseCode are:

  • 0: Success; The subscription is deleted.
  • 17: No subscription existed; No matching Topic Filter is being used by the Client.
  • 128: Unspecified error; The unsubscribe could not be completed and the Server either does not wish to reveal the reason or none of the other Reason Codes apply.
  • 131: Implementation specific error; The UNSUBSCRIBE is valid but the Server does not accept it.
  • 135: Not authorized; The Client is not authorized to unsubscribe.
  • 143: Topic Filter invalid; The Topic Filter is correctly formed but is not allowed for this Client.
  • 145: Packet Identifier in use; The specified Packet Identifier is already in use.

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