Table of Contents

Class MqttApplicationMessage

Namespace
MQTTnet
Assembly
MQTTnet.dll
public sealed class MqttApplicationMessage
Inheritance
MqttApplicationMessage
Inherited Members
Extension Methods

Constructors

MqttApplicationMessage() 

public MqttApplicationMessage()

Properties

ContentType

Gets or sets the content type. The content type must be a UTF-8 encoded string. The content type value identifies the kind of UTF-8 encoded payload.

public string ContentType { get; set; }

Property Value

string

CorrelationData

Gets or sets the correlation data. In order for the sender to know what sent message the response refers to it can also send correlation data with the published message. Hint: MQTT 5 feature only.

public byte[] CorrelationData { get; set; }

Property Value

byte[]

Dup

If the DUP flag is set to 0, it indicates that this is the first occasion that the Client or Server has attempted to send this MQTT PUBLISH Packet. If the DUP flag is set to 1, it indicates that this might be re-delivery of an earlier attempt to send the Packet. The DUP flag MUST be set to 1 by the Client or Server when it attempts to re-deliver a PUBLISH Packet [MQTT-3.3.1.-1]. The DUP flag MUST be set to 0 for all QoS 0 messages [MQTT-3.3.1-2].

public bool Dup { get; set; }

Property Value

bool

MessageExpiryInterval

Gets or sets the message expiry interval. A client can set the message expiry interval in seconds for each PUBLISH message individually. This interval defines the period of time that the broker stores the PUBLISH message for any matching subscribers that are not currently connected. When no message expiry interval is set, the broker must store the message for matching subscribers indefinitely. When the retained=true option is set on the PUBLISH message, this interval also defines how long a message is retained on a topic. Hint: MQTT 5 feature only.

public uint MessageExpiryInterval { get; set; }

Property Value

uint

Payload

Gets or sets the payload. The payload is the data bytes sent via the MQTT protocol.

[Obsolete("Use PayloadSegment instead. This property will be removed in a future release.")]
public byte[] Payload { get; set; }

Property Value

byte[]

PayloadFormatIndicator

Gets or sets the payload format indicator. The payload format indicator is part of any MQTT packet that can contain a payload. The indicator is an optional byte value. A value of 0 indicates an “unspecified byte stream”. A value of 1 indicates a "UTF-8 encoded payload". If no payload format indicator is provided, the default value is 0. Hint: MQTT 5 feature only.

public MqttPayloadFormatIndicator PayloadFormatIndicator { get; set; }

Property Value

MqttPayloadFormatIndicator

PayloadSegment

Get or set ArraySegment style of Payload.

public ArraySegment<byte> PayloadSegment { get; set; }

Property Value

ArraySegment<byte>

QualityOfServiceLevel

Gets or sets the quality of service level. The Quality of Service (QoS) level is an agreement between the sender of a message and the receiver of a message that defines the guarantee of delivery for a specific message. There are 3 QoS levels in MQTT:

  • At most once (0): Message gets delivered no time, once or multiple times.
  • At least once (1): Message gets delivered at least once (one time or more often).
  • Exactly once (2): Message gets delivered exactly once (It's ensured that the message only comes once).
public MqttQualityOfServiceLevel QualityOfServiceLevel { get; set; }

Property Value

MqttQualityOfServiceLevel

ResponseTopic

Gets or sets the response topic. In MQTT 5 the ability to publish a response topic was added in the publish message which allows you to implement the request/response pattern between clients that is common in web applications. Hint: MQTT 5 feature only.

public string ResponseTopic { get; set; }

Property Value

string

Retain

Gets or sets a value indicating whether the message should be retained or not. A retained message is a normal MQTT message with the retained flag set to true. The broker stores the last retained message and the corresponding QoS for that topic.

public bool Retain { get; set; }

Property Value

bool

SubscriptionIdentifiers

Gets or sets the subscription identifiers. The client can specify a subscription identifier when subscribing. The broker will establish and store the mapping relationship between this subscription and subscription identifier when successfully create or modify subscription. The broker will return the subscription identifier associated with this PUBLISH packet and the PUBLISH packet to the client when need to forward PUBLISH packets matching this subscription to this client. Hint: MQTT 5 feature only.

public List<uint> SubscriptionIdentifiers { get; set; }

Property Value

List<uint>

Topic

Gets or sets the MQTT topic. In MQTT, the word topic refers to an UTF-8 string that the broker uses to filter messages for each connected client. The topic consists of one or more topic levels. Each topic level is separated by a forward slash (topic level separator).

public string Topic { get; set; }

Property Value

string

TopicAlias

Gets or sets the topic alias. Topic aliases were introduced are a mechanism for reducing the size of published packets by reducing the size of the topic field. A value of 0 indicates no topic alias is used. Hint: MQTT 5 feature only.

public ushort TopicAlias { get; set; }

Property Value

ushort

UserProperties

Gets or sets the user properties. In MQTT 5, user properties are basic UTF-8 string key-value pairs that you can append to almost every type of MQTT packet. As long as you don’t exceed the maximum message size, you can use an unlimited number of user properties to add metadata to MQTT messages and pass information between publisher, broker, and subscriber. The feature is very similar to the HTTP header concept. Hint: MQTT 5 feature only.

public List<MqttUserProperty> UserProperties { get; set; }

Property Value

List<MqttUserProperty>