MessageIn Event

Fired when an incoming message has been received and/or fully acknowledged.

Syntax

• C++
• Objective-C
• C

ANSI (Cross Platform)
virtual int FireMessageIn(MQTTMessageInEventParams *e);

typedef struct {
  int PacketId;
  const char *Topic;
  int QOS;
  const char *Message;
  int lenMessage;
  int Retained;
  int Duplicate;
  int reserved;
} MQTTMessageInEventParams;

Unicode (Windows)
virtual INT FireMessageIn(MQTTMessageInEventParams *e);

typedef struct {
  INT PacketId;
  LPCWSTR Topic;
  INT QOS;
  LPCSTR Message;
  INT lenMessage;
  BOOL Retained;
  BOOL Duplicate;
  INT reserved;
} MQTTMessageInEventParams;

- (void)onMessageIn:(int)packetId :(NSString*)topic :(int)QOS :(NSData*)message :(BOOL)retained :(BOOL)duplicate;

#define EID_MQTT_MESSAGEIN 7

virtual INT IPWORKSIOT_CALL FireMessageIn(INT &iPacketId, LPSTR &lpszTopic, INT &iQOS, LPSTR &lpMessage, INT &lenMessage, BOOL &bRetained, BOOL &bDuplicate);

Remarks

The MessageIn event fires once for each incoming message either immediately after it is received (QoS 0), or after it has been fully acknowledged (QoS 1 and 2).

• PacketId: The message packet Id. This will always be -1 if QOS is 0.
• Topic: The message's topic string.
• QOS: The message's QoS level.
• Message: The message data.
• Retained: Whether or not this message was received as a result of subscribing to a topic.
• Duplicate: Whether or not the server has indicated that this message is a duplicate of another message sent previously.

Refer to MessageAck for more information about QoS 1 and 2 message processing steps.

// MessageIn event handler.
mqtt1.OnMessageIn += (s, e) => {
  Console.WriteLine("Received message from topic '" + e.Topic + "' with QoS " + e.QOS + ":");
  Console.WriteLine(e.Message);
};