Implemented new event consumer examples and fixed some bugs with it.

examples/CMakeLists.txt

@@ -33,6 +33,8 @@ set(EXECUTABLES
     async_subscribe
     async_consume
     async_consume_v5
+    async_message_consume
+    async_message_consume_v5
     data_publish
     mqttpp_chat
     multithr_pub_sub

examples/async_consume.cpp

@@ -62,12 +62,6 @@ int main(int argc, char* argv[])
                         .automatic_reconnect()
                         .finalize();
 
-    // The client will handle automatic reconnects, but we add this
-    // callbacks to let the user know when we're reconnected.
-    cli.set_connected_handler([](const std::string&) {
-        cout << "\n*** Connected ***" << endl;
-    });
-
     try {
         // Start consumer before connecting to make sure to not miss any messages
 
@@ -96,13 +90,22 @@ int main(int argc, char* argv[])
 
         cout << "\nWaiting for messages on topic: '" << TOPIC << "'" << endl;
 
+        // The client handles automatic reconnects, but we monitor
+        // the events here to report them to the user.
         while (true) {
-            auto msg = cli.consume_message();
-
-            if (msg)
-                cout << msg->get_topic() << ": " << msg->to_string() << endl;
-            else
+            auto evt = cli.consume_event();
+
+            if (const auto* p = std::get_if<mqtt::message_arrived_event>(&evt)) {
+                auto& msg = p->msg;
+                if (msg)
+                    cout << msg->get_topic() << ": " << msg->to_string() << endl;
+            }
+            else if (std::holds_alternative<mqtt::connected_event>(evt))
+                cout << "\n*** Connected ***" << endl;
+            else if (std::holds_alternative<mqtt::connection_lost_event>(evt))
                 cout << "*** Connection Lost ***" << endl;
+            else
+                cout << "???" << endl;
         }
     }
     catch (const mqtt::exception& exc) {

examples/async_consume_v5.cpp

@@ -60,15 +60,6 @@ int main(int argc, char* argv[])
                         .finalize();
 
     try {
-        cli.set_connection_lost_handler([](const std::string&) {
-            cout << "*** Connection Lost ***" << endl;
-        });
-
-        cli.set_disconnected_handler([](const mqtt::properties&, mqtt::ReasonCode reason) {
-            cout << "*** Disconnected. Reason [0x" << hex << int{reason} << "]: " << reason
-                 << " ***" << endl;
-        });
-
         // Start consumer before connecting to make sure to not miss messages
 
         cli.start_consuming();
@@ -105,10 +96,26 @@ int main(int argc, char* argv[])
         cout << "\nWaiting for messages on topic: '" << TOPIC << "'" << endl;
 
         while (true) {
-            auto msg = cli.consume_message();
-            if (!msg)
+
+            auto evt = cli.consume_event();
+
+            if (const auto* p = std::get_if<mqtt::message_arrived_event>(&evt)) {
+                auto& msg = p->msg;
+                if (msg)
+                    cout << msg->get_topic() << ": " << msg->to_string() << endl;
+            }
+            else if (std::holds_alternative<mqtt::connected_event>(evt)) {
+                cout << "\n*** Connected ***" << endl;
+            }
+            else if (std::holds_alternative<mqtt::connection_lost_event>(evt)) {
+                cout << "*** Connection Lost ***" << endl;
                 break;
-            cout << msg->get_topic() << ": " << msg->to_string() << endl;
+            }
+            else if (const auto* p = std::get_if<mqtt::disconnected_event>(&evt)) {
+                cout << "*** Disconnected. Reason [0x" << hex << int{p->reasonCode}
+                    << "]: " << p->reasonCode << " ***" << endl;
+                break;
+            }
         }
 
         // If we're here, the client was almost certainly disconnected.
@@ -120,9 +127,6 @@ int main(int argc, char* argv[])
             cli.disconnect()->wait();
             cout << "OK" << endl;
         }
-        else {
-            cout << "\nClient was disconnected" << endl;
-        }
     }
     catch (const mqtt::exception& exc) {
         cerr << "\n  " << exc << endl;

src/async_client.cpp

@@ -857,8 +857,9 @@ void async_client::start_consuming()
         nullptr
     );
 
-    if (rc != MQTTASYNC_SUCCESS)
-        throw exception(rc);
+    check_ret(rc);
+    check_ret(::MQTTAsync_setConnected(cli_, this, &async_client::on_connected));
+    check_ret(::MQTTAsync_setDisconnected(cli_, this, &async_client::on_disconnected));
 }
 
 void async_client::stop_consuming()