| .TH "MQTTAsync_message" 3 "Thu Sep 13 2018" "Paho Asynchronous MQTT C Client Library" \" -*- nroff -*- |
| .ad l |
| .nh |
| .SH NAME |
| MQTTAsync_message |
| .SH SYNOPSIS |
| .br |
| .PP |
| .PP |
| \fC#include <MQTTAsync\&.h>\fP |
| .SS "Data Fields" |
| |
| .in +1c |
| .ti -1c |
| .RI "char \fBstruct_id\fP [4]" |
| .br |
| .ti -1c |
| .RI "int \fBstruct_version\fP" |
| .br |
| .ti -1c |
| .RI "int \fBpayloadlen\fP" |
| .br |
| .ti -1c |
| .RI "void * \fBpayload\fP" |
| .br |
| .ti -1c |
| .RI "int \fBqos\fP" |
| .br |
| .ti -1c |
| .RI "int \fBretained\fP" |
| .br |
| .ti -1c |
| .RI "int \fBdup\fP" |
| .br |
| .ti -1c |
| .RI "int \fBmsgid\fP" |
| .br |
| .ti -1c |
| .RI "\fBMQTTProperties\fP \fBproperties\fP" |
| .br |
| .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 MQTTAsync_publishMessage(), MQTTAsync_publish(), MQTTAsync_receive(), \fBMQTTAsync_freeMessage()\fP and \fBMQTTAsync_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: |
| .IP "\fB\fBQoS0\fP \fP" 1c |
| Fire and forget - the message may not be delivered |
| .IP "\fB\fBQoS1\fP \fP" 1c |
| At least once - the message will be delivered, but may be delivered more than once in some circumstances\&. |
| .IP "\fB\fBQoS2\fP \fP" 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 |
| .br |
| 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 |
| .br |
| 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 Asynchronous MQTT C Client Library from the source code\&. |
