I configured the example to connect to the test server "tcp://test.mosquitto.org:1883" This is the output:

$ ./src/samples/async_subscribe Connecting to the MQTT server... Connection success

Subscribing to topic 'hello' for client async_subcribe_cpp using QoS1

Press Q to quit

Connection success

Subscribing to topic 'hello' for client async_subcribe_cpp using QoS1

Press Q to quit

Subscription success for token: [1] token topic: 'hello', ...

Message arrived topic: 'hello' payload: 'hi'

Subscription success for token: [2] token topic: 'hello', ...

Message arrived topic: 'hello' payload: 'hi'

Message arrived topic: 'hello' payload: 'snsfgsnb'

Q

Hello, I have built a project before using this with no issues.

However, now I am getting this error:

[ ERROR ] [ ERROR ] MQTT error [-8]: Bad structure

When calling this:

        std::string address = "tcp://192.168.1.51:1883";
        std::string client = "some-client";

        mqtt::async_client cli(address, client);

I have absolutely no idea why this is failing like this. I have followed the instructions exactly as described in the readme for building both paho.mqtt.c and paho.mqtt.cpp.

Any ideas on why this might be happening?

When monitoring some processes of mine, I recognized a slowly inreasing memory usage over time.
So after quite some time of debugging, it looks like there is some sort of memory leak in the library.
More specifically, memory increases only when I subscribe to a topic and messages are incoming. In the PAHO C lib I dont see this leak.

I added my test code, so you can try out. Let it run for a minute and memory usage should be up.

The dummy_callback_listener does nothing with the message itself, just an empty callback.

getMemoryUsage gets its data from ifstream stat_stream("/proc/self/stat",ios_base::in);

Hope you can help me out here.

PAHO CPP VERSION "1.0.1" PAHO C VERSION "1.3.0"
Ubuntu 18.04

   mqtt::connect_options connectOptions;

   std::unique_ptr<mqtt::async_client>asyncClient = std::make_unique<mqtt::async_client>( mqtt::SERVER_ADDRESS, "MemoryRawClientTests" );
   auto conntok = asyncClient->connect( connectOptions );
   conntok->wait();
   asyncClient->start_consuming();

   dummy_callback_listener callbackListener;
   asyncClient->set_callback(callbackListener);

   dummy_action_listener listener;
   asyncClient->subscribe(mqtt::SERVER_TOPIC, 0, nullptr, listener);

   std::string payload = "SimpleMessageCallbackTestSimpleMessageCallbackTestSimpleMessageCallbackTestSimpleMessageCallbackTestSimpleMessageCallbackTest";
   mqtt::message_ptr message = mqtt::make_message(mqtt::SERVER_TOPIC, payload.c_str(), payload.size());

   while (true)
   {
      asyncClient->publish(message);
      log_info("mem usage: {}", getMemoryUsageString() );
      std::this_thread::sleep_for(10ms);
   }

I'm using the synchronous client, but I still need to set a callback class in order to handle the incoming messages in an asynchronous way. I think it would be easier if the own client worked as a socket, buffering all the incoming messages. The client class would have a "receive" method or so, which pops the next message from the queue. If it's empty, it could block for some timeout period that would be passed as an argument.

Hi

Where can i get it? Currently we use the non-secure version on: https://github.com/eclipse/paho.mqtt.cpp.git

But now we need the version that supports SSL / TLS...

Thank you for your feedbacks...

With kind regards, Jan

Hi guys,

I am trying to connect to my mosquitto server using c++ on my mac and I am getting this error :

123145416470528:error:14094410:SSL routines:ssl3_read_bytes:sslv3 alert handshake failure:s3_pkt.c:1500:SSL alert number 40
MQTT error [-1]: TCP/TLS connect failure

I am using the same certificates I am using on my raspberry pi which is currently running and publishing data.

This is the code I use right now. I scrapped it from tests and samples.

 try{
        mqtt::client client(ADDRESS, "10");
        mqtt::connect_options connOpts;
        mqtt::ssl_options sslOptions;
        sslOptions.set_trust_store("/Users/jefflabonte/Documents/Development/Projects/MyProject/certificates/device001_certs/mycert.pem");
//        sslOptions.set_key_store("/Users/jefflabonte/Documents/Development/Projects/MyProject/certificates/device001_certs/device001.crt");
        connOpts.set_ssl(sslOptions);
        connOpts.set_mqtt_version(MQTTVERSION_3_1_1);
        connOpts.set_keep_alive_interval(20);
        connOpts.set_clean_session(true);

        client.connect(connOpts);

    }catch(mqtt::exception ex){
        std::cerr << ex.to_string() << std::endl;

    }

Any idea on what I did wrong?

CMake for the C++ library is asking for version 3.1. Is there anything significant that would need to be done to support slightly older versions of CMake, perhaps back to version 2.8?

This is the version that comes with Ubuntu 14.04 LTS, Linux Mint 17 LTS, and (I believe) the latest Raspberry Pi Raspbian, Nvidia TX1, and a number of other embedded Linux boards. These could use autotools or Make, but it would be nice to have CMake work for them as it is likely to became the default build standard.

[ubuntu-14.04] $ cmake ..
CMake Error at CMakeLists.txt:20 (cmake_minimum_required):
  CMake 3.1 or higher is required.  You are running version 2.8.12.2

-- Configuring incomplete, errors occurred!

@guilhermeferreira

Hi,

I encountered a problem when compiling the sample c++ code. It seems lack of libraries files. Is it because there's no "make install" option to add those libraries into system path?

I also tried paho.mqtt.c, that compile has no issue happen.

jason2015@ubuntu:~/mqtt/paho.mqtt.cpp/src/samples$ make sync_publish g++ -I.. -I/home/fmp/static/opensrc/mqtt/paho/org.eclipse.paho.mqtt.c/src -D_NDEBUG -Wall -std=c++0x -O2 -o sync_publish sync_publish.cpp -L../lib -L/home/fmp/static/opensrc/mqtt/paho/org.eclipse.paho.mqtt.c/src/linux_ia64 -lmqttpp -lmqttv3a /usr/bin/ld: cannot find -lmqttv3a collect2: error: ld returned 1 exit status make: *** [sync_publish] Error 1

Best Regards!

Modernize the CMake build system, including the generation and installation of a CMake package configuration file. This will make it easier for CMake-enabled projects to use paho.mqtt.cpp: they'll just have to call find_package(PahoMqttCpp) and then have their targets link against PahoMqttCpp::paho-mqttpp3.

Also, remove the other build systems because maintaining multiple build systems is painful.

Hello, I've been using the MQTT c++ library with success but I do not understand how the mqtt::client_ptr works.

I see that it's a shared pointer, but how do I instantiate it? the constructor is deleted, and std::make_sharedmqtt::client() doesn't work as well.

I can not find any info

is it recommended to stay with paho.mqtt.c 1.3.1 ? there have been quite some changes, and I guess fixes and improvements since this version in paho.mqtt.c

Let's say you have a scenario like this:

async_client client{ MY_PARAMETERS };
client.disconnect(MY_TIMEOUT)->set_action_callback(MY_LISTENER);

In this case it is possible that the disconnect finishes before the listener is set internally. When that happens the listener is never called anymore.

Would it be acceptable from your side to, IF the token was already completed, call the listener directly when it is set? From a user side it is hard to do this thread safe, but you have the locks in place to allow it. A PR will come tomorrow and then you can decide!

Currently, the CMake finds paho.mqtt.c with a shim FindPahoMqttC.cmake file. This calls find_library on the desired library name, and manually calls find_path on MQTTAsync.h.

Why do we go through this effort when paho.mqtt.c already exports a config file (eclipse-paho-mqtt-cConfig.cmake) that exports its targets?

Basically my thought is that we should change find_package(PahoMqttC) to find_package(eclipse-paho-mqtt-c).

If there is a technical/historical reason for this that I am missing, please let me know. I'm new to the project.

Hello, I use this library to set the heartbeat interval to 2 minutes. Why is the ConnectLost callback activated quickly when the network is unavailable? Sometimes it takes more than 2 minutes to activate.

Hello,

I use the mqtt::client to connect to an MQTT broker and then, in a different thread, I call regularly the function client.try_consume_message_for(&message_ptr, std::chrono::seconds{1}). If the function returns false, I attempt a reconnect and if it returns true, I handle the message. Now if the broker disconnect remotely and the client is currently within the call try_consume_message_for, the call returns with the value true and with message_ptr set to nullptr. I think, the call should return with false if the message_ptr value is not set (or set to nullptr). The next call(s) to try_consume_message_for returns false as expected. Rough example:

class MyClass {
   void MyClass(mqtt::connect_options options) {
      client_ = std::make_unique<mqtt::client>("host", "client_id");
      client_->start_consuming();

      client_->connect(options);
      thread_ = std::thread {
         mqtt::const_message_ptr mqtt_message;
         while (true) {
            if (!client_->try_consume_message_for(&mqtt_message, std::chrono::seconds{1})) {
                 print("disconnected... attempt reconnect");
                 // add code to reconnect
                 continue;
             }
             
              auto payload = mqtt_message->get_payload(); // this crashes on disconnect since try_consume_message_for returned true
         }
      };
   }

   std::unique_ptr<mqtt::client> client_;
   std::thread thread_;
}

I'm trying to compile following the instructions in the readme but it fails with Could NOT find PahoMqttC (missing: PAHO_MQTT_C_LIBRARIES):

C:\Users\Matteo\Documents\paho.mqtt.cpp>cmake -Bbuild -H. -DCMAKE_INSTALL_PREFIX=C:\mqtt\paho-cpp -DPAHO_BUILD_SAMPLES=ON -DPAHO_WITH_SSL=OFF -DCMAKE_PREFIX_PATH=C:\mqtt\paho-c
-- Building for: Visual Studio 17 2022
-- The CXX compiler identification is MSVC 19.33.31630.0
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: C:/Program Files/Microsoft Visual Studio/2022/Community/VC/Tools/MSVC/14.33.31629/bin/Hostx64/x64/cl.exe - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
CMake Error at C:/Program Files/CMake/share/cmake-3.24/Modules/FindPackageHandleStandardArgs.cmake:230 (message):
  Could NOT find PahoMqttC (missing: PAHO_MQTT_C_LIBRARIES)
Call Stack (most recent call first):
  C:/Program Files/CMake/share/cmake-3.24/Modules/FindPackageHandleStandardArgs.cmake:594 (_FPHSA_FAILURE_MESSAGE)
  cmake/FindPahoMqttC.cmake:33 (FIND_PACKAGE_HANDLE_STANDARD_ARGS)
  src/CMakeLists.txt:26 (find_package)


-- Configuring incomplete, errors occurred!
See also "C:/Users/Matteo/Documents/paho.mqtt.cpp/build/CMakeFiles/CMakeOutput.log".

Checking the CMakeList.txt file in src it is possible to see that the find_package instruction search for what seems to be the wrong package name: https://github.com/eclipse/paho.mqtt.cpp/blob/master/src/CMakeLists.txt#L26 :

find_package(PahoMqttC REQUIRED)

While, according to the README of the C library you should use a different package name https://github.com/eclipse/paho.mqtt.c#building-your-application-with-cmake :

find_package(eclipse-paho-mqtt-c REQUIRED)

And a test build with this change leads to a different error:

C:\Users\Matteo\Documents\paho.mqtt.cpp>cmake -Bbuild -H. -DCMAKE_INSTALL_PREFIX=C:\mqtt\paho-cpp -DPAHO_BUILD_SAMPLES=ON -DPAHO_WITH_SSL=OFF -DCMAKE_PREFIX_PATH=C:\mqtt\paho-c
-- Performing Test CMAKE_HAVE_LIBC_PTHREAD
-- Performing Test CMAKE_HAVE_LIBC_PTHREAD - Failed
-- Check if compiler accepts -pthread
-- Check if compiler accepts -pthread - no
-- Looking for pthread_create in pthreads
-- Looking for pthread_create in pthreads - not found
-- Looking for pthread_create in pthread
-- Looking for pthread_create in pthread - not found
-- Found Threads: TRUE
-- Configuring done
CMake Error at src/CMakeLists.txt:126 (target_link_libraries):
  Target "paho-mqttpp3-static" links to:

    PahoMqttC::PahoMqttC

  but the target was not found.  Possible reasons include:

    * There is a typo in the target name.
    * A find_package call is missing for an IMPORTED target.
    * An ALIAS target is missing.



-- Generating done
CMake Generate step failed.  Build files cannot be regenerated correctly.

Updating the target_link_libraries according to the documentation of the C library (line 126):

    ## add dependencies to the shared library
    target_link_libraries(paho-mqttpp3-static
        PRIVATE ${LIBS_SYSTEM}
        PUBLIC eclipse-paho-mqtt-c::paho-mqtt3a Threads::Threads)

CMake can create the build files correctly:

C:\Users\Matteo\Documents\paho.mqtt.cpp>cmake -Bbuild -H. -DCMAKE_INSTALL_PREFIX=C:\mqtt\paho-cpp -DPAHO_BUILD_SAMPLES=ON -DPAHO_WITH_SSL=OFF -DCMAKE_PREFIX_PATH=C:\mqtt\paho-c
-- Building for: Visual Studio 17 2022
-- The CXX compiler identification is MSVC 19.33.31630.0
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: C:/Program Files/Microsoft Visual Studio/2022/Community/VC/Tools/MSVC/14.33.31629/bin/Hostx64/x64/cl.exe - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Performing Test CMAKE_HAVE_LIBC_PTHREAD
-- Performing Test CMAKE_HAVE_LIBC_PTHREAD - Failed
-- Check if compiler accepts -pthread
-- Check if compiler accepts -pthread - no
-- Looking for pthread_create in pthreads
-- Looking for pthread_create in pthreads - not found
-- Looking for pthread_create in pthread
-- Looking for pthread_create in pthread - not found
-- Found Threads: TRUE
-- Configuring done
-- Generating done
-- Build files have been written to: C:/Users/Matteo/Documents/paho.mqtt.cpp/build

But the system cannot actually build:

C:\Users\Matteo\Documents\paho.mqtt.cpp>cmake --build build/ --target install
MSBuild version 17.3.1+2badb37d1 for .NET Framework
  Building Custom Rule C:/Users/Matteo/Documents/paho.mqtt.cpp/src/CMakeLists.txt
  async_client.cpp
C:\Users\Matteo\Documents\paho.mqtt.cpp\src\mqtt/async_client.h(28,10): fatal  error C1083: Cannot open include file: 'MQTTAsync.h': No such file or directory [C:\Users\Matteo\Doc
uments\paho.mqtt.cpp\build\src\paho-cpp-objs.vcxproj]
  client.cpp
C:\Users\Matteo\Documents\paho.mqtt.cpp\src\mqtt/async_client.h(28,10): fatal  error C1083: Cannot open include file: 'MQTTAsync.h': No such file or directory [C:\Users\Matteo\Doc
uments\paho.mqtt.cpp\build\src\paho-cpp-objs.vcxproj]
  connect_options.cpp
C:\Users\Matteo\Documents\paho.mqtt.cpp\src\mqtt/connect_options.h(27,10): fatal  error C1083: Cannot open include file: 'MQTTAsync.h': No such file or directory [C:\Users\Matteo\
Documents\paho.mqtt.cpp\build\src\paho-cpp-objs.vcxproj]
  create_options.cpp
C:\Users\Matteo\Documents\paho.mqtt.cpp\src\mqtt/create_options.h(27,10): fatal  error C1083: Cannot open include file: 'MQTTAsync.h': No such file or directory [C:\Users\Matteo\D
ocuments\paho.mqtt.cpp\build\src\paho-cpp-objs.vcxproj]
  disconnect_options.cpp
C:\Users\Matteo\Documents\paho.mqtt.cpp\src\mqtt/disconnect_options.h(26,10): fatal  error C1083: Cannot open include file: 'MQTTAsync.h': No such file or directory [C:\Users\Matt
eo\Documents\paho.mqtt.cpp\build\src\paho-cpp-objs.vcxproj]
  iclient_persistence.cpp
C:\Users\Matteo\Documents\paho.mqtt.cpp\src\mqtt/iclient_persistence.h(27,10): fatal  error C1083: Cannot open include file: 'MQTTAsync.h': No such file or directory [C:\Users\Mat
teo\Documents\paho.mqtt.cpp\build\src\paho-cpp-objs.vcxproj]
  message.cpp
C:\Users\Matteo\Documents\paho.mqtt.cpp\src\mqtt/message.h(28,10): fatal  error C1083: Cannot open include file: 'MQTTAsync.h': No such file or directory [C:\Users\Matteo\Document
s\paho.mqtt.cpp\build\src\paho-cpp-objs.vcxproj]
  properties.cpp
C:\Users\Matteo\Documents\paho.mqtt.cpp\src\mqtt/properties.h(28,11): fatal  error C1083: Cannot open include file: 'MQTTProperties.h': No such file or directory [C:\Users\Matteo\
Documents\paho.mqtt.cpp\build\src\paho-cpp-objs.vcxproj]
  response_options.cpp
C:\Users\Matteo\Documents\paho.mqtt.cpp\src\mqtt/response_options.h(10,10): fatal  error C1083: Cannot open include file: 'MQTTAsync.h': No such file or directory [C:\Users\Matteo
\Documents\paho.mqtt.cpp\build\src\paho-cpp-objs.vcxproj]
  ssl_options.cpp
C:\Users\Matteo\Documents\paho.mqtt.cpp\src\mqtt/ssl_options.h(30,10): fatal  error C1083: Cannot open include file: 'MQTTAsync.h': No such file or directory [C:\Users\Matteo\Docu
ments\paho.mqtt.cpp\build\src\paho-cpp-objs.vcxproj]
  string_collection.cpp
C:\Users\Matteo\Documents\paho.mqtt.cpp\src\mqtt/string_collection.h(27,10): fatal  error C1083: Cannot open include file: 'MQTTAsync.h': No such file or directory [C:\Users\Matte
o\Documents\paho.mqtt.cpp\build\src\paho-cpp-objs.vcxproj]
  subscribe_options.cpp
C:\Users\Matteo\Documents\paho.mqtt.cpp\src\mqtt/subscribe_options.h(27,10): fatal  error C1083: Cannot open include file: 'MQTTAsync.h': No such file or directory [C:\Users\Matte
o\Documents\paho.mqtt.cpp\build\src\paho-cpp-objs.vcxproj]
  token.cpp
C:\Users\Matteo\Documents\paho.mqtt.cpp\src\mqtt/token.h(28,10): fatal  error C1083: Cannot open include file: 'MQTTAsync.h': No such file or directory [C:\Users\Matteo\Documents\
paho.mqtt.cpp\build\src\paho-cpp-objs.vcxproj]
  topic.cpp
C:\Users\Matteo\Documents\paho.mqtt.cpp\src\mqtt/topic.h(27,10): fatal  error C1083: Cannot open include file: 'MQTTAsync.h': No such file or directory [C:\Users\Matteo\Documents\
paho.mqtt.cpp\build\src\paho-cpp-objs.vcxproj]
  will_options.cpp
C:\Users\Matteo\Documents\paho.mqtt.cpp\src\mqtt/will_options.h(29,10): fatal  error C1083: Cannot open include file: 'MQTTAsync.h': No such file or directory [C:\Users\Matteo\Doc
uments\paho.mqtt.cpp\build\src\paho-cpp-objs.vcxproj]
  Generating Code...

What should I do?