TsgcWSPClient_MQTT › Events › OnMQTTUnSubscribe

OnMQTTUnSubscribe Event

Fires when an UNSUBACK is received in response to UnSubscribe; exposes per-topic reason codes and MQTT 5 UnsubscribeProperties.

Syntax

property OnMQTTUnSubscribe: TsgcWSMQTTUnSubscribeEvent;
// TsgcWSMQTTUnSubscribeEvent = procedure(Connection: TsgcWSConnection; aPacketIdentifier: Word; aCodes: TsgcWSUNSUBACKS; UnsubscribeProperties: TsgcWSMQTTUNSUBACKProperties) of object

Default Value

—

Remarks

Raised when the broker replies with an UNSUBACK to an UNSUBSCRIBE request. In MQTT 3.1.1 UNSUBACK carries no status; in MQTT 5.0 it carries one reason code per topic filter so the server can report "no subscription existed" or "not authorized" per-topic. Parameters:

• aPacketIdentifier — 16-bit packet id of the original UNSUBSCRIBE.
• aCodes — a TsgcWSUNSUBACKS array with one entry per topic filter (MQTT 5). Typical values: 0 = Success, 0x11 = No subscription existed, 0x87 = Not authorized.
• UnsubscribeProperties (MQTT 5) — UserProperties returned by the broker.

Example

procedure TForm1.MQTTUnSubscribe(Connection: TsgcWSConnection;
  aPacketIdentifier: Word; aCodes: TsgcWSUNSUBACKS;
  UnsubscribeProperties: TsgcWSMQTTUNSUBACKProperties);
var
  i: Integer;
begin
  for i := 0 to Length(aCodes) - 1 do
    Memo1.Lines.Add(Format('unsubscribe %d result=$%x',
      [i, aCodes[i]]));
end;

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