.TH "MQTTClient_message" 3 "Sat Aug 16 2025 14:15:23" "Paho MQTT C Client Library" \" -*- nroff -*-
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.SH NAME
MQTTClient_message
.SH SYNOPSIS
.br
.PP
.PP
\fR#include <MQTTClient\&.h>\fP
.SS "Data Fields"

.in +1c
.ti -1c
.RI "char \fBstruct_id\fP [4]"
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.ti -1c
.RI "int \fBstruct_version\fP"
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.RI "int \fBpayloadlen\fP"
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.ti -1c
.RI "void * \fBpayload\fP"
.br
.ti -1c
.RI "int \fBqos\fP"
.br
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.RI "int \fBretained\fP"
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.RI "int \fBdup\fP"
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.RI "int \fBmsgid\fP"
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.RI "\fBMQTTProperties\fP \fBproperties\fP"
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.in -1c
.SH "Detailed Description"
.PP 
A structure representing the payload and attributes of an MQTT message\&. The message topic is not part of this structure (see \fBMQTTClient_publishMessage()\fP, \fBMQTTClient_publish()\fP, \fBMQTTClient_receive()\fP, \fBMQTTClient_freeMessage()\fP and \fBMQTTClient_messageArrived()\fP)\&. 
.SH "Field Documentation"
.PP 
.SS "char struct_id[4]"
The eyecatcher for this structure\&. must be MQTM\&. 
.SS "int struct_version"
The version number of this structure\&. Must be 0 or 1 0 indicates no message properties 
.SS "int payloadlen"
The length of the MQTT message payload in bytes\&. 
.SS "void* payload"
A pointer to the payload of the MQTT message\&. 
.SS "int qos"
The quality of service (QoS) assigned to the message\&. There are three levels of QoS: 

.PP
.IP "\fB\fBQoS0\fP 
.IP "" 1c
Fire and forget - the message may not be delivered 

.PP
.IP "\fB\fBQoS1\fP 
.IP "" 1c
At least once - the message will be delivered, but may be delivered more than once in some circumstances\&. 

.PP
.IP "\fB\fBQoS2\fP 
.IP "" 1c
Once and one only - the message will be delivered exactly once\&. 

.PP

.SS "int retained"
The retained flag serves two purposes depending on whether the message it is associated with is being published or received\&.

.PP
\fBretained = true\fP
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 For messages being published, a true setting indicates that the MQTT server should retain a copy of the message\&. The message will then be transmitted to new subscribers to a topic that matches the message topic\&. For subscribers registering a new subscription, the flag being true indicates that the received message is not a new one, but one that has been retained by the MQTT server\&.

.PP
\fBretained = false\fP 
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 For publishers, this indicates that this message should not be retained by the MQTT server\&. For subscribers, a false setting indicates this is a normal message, received as a result of it being published to the server\&. 
.SS "int dup"
The dup flag indicates whether or not this message is a duplicate\&. It is only meaningful when receiving QoS1 messages\&. When true, the client application should take appropriate action to deal with the duplicate message\&. 
.SS "int msgid"
The message identifier is normally reserved for internal use by the MQTT client and server\&. 
.SS "\fBMQTTProperties\fP properties"
The MQTT V5 properties associated with the message\&. 

.SH "Author"
.PP 
Generated automatically by Doxygen for Paho MQTT C Client Library from the source code\&.