Problems linking a very simple MQTT client (Azure IOT Hub SDK)

Question

I followed the offical documentation and the MS Azure IOT SDK for C guide described here

https://learn.microsoft.com/de-de/azure/iot-hub/iot-hub-device-sdk-c-intro

to build my very simple own client to send MQTT messages. But on a ubuntu machine I am not able to get this client to work. Compiling and linking is done with cmake and make. But the make VERBOSE=1 command runs in "undefined reference" errors (see screenshot). I thought all libraries were available in the system after installing the SDK via apt-get. But now it seems so, that some are missing. Could you give me an information about what libs are missing or a way to find out which are non existent (maybe one is the parson lib)? This is the make/linker output (only some lines of some more lines):

/usr/bin/cmake -E cmake_link_script CMakeFiles/mqttsender.dir/link.txt --verbose=1 /usr/bin/cc -rdynamic CMakeFiles/mqttsender.dir/mqttsender.c.o -o mqttsender -liothub_client -liothub_client_mqtt_transport -laziotsharedutil -lssl -lpthread -lcurl -lssl -lcrypto -lm -lpthread -lcurl -lcrypto -lm /usr/lib/gcc/x86_64-linux-gnu/7/../../../../lib/libiothub_client.a(iothub_client_ll_uploadtoblob.c.o): In function parse_result_json': iothub_client_ll_uploadtoblob.c:(.text+0x334): undefined reference tojson_parse_string'" /usr/lib/gcc/x86_64-linux-gnu/7/../../../../lib/libiothub_client_mqtt_transport.a(iothubtransport_mqtt_common.c.o): In function free_transport_handle_data': iothubtransport_mqtt_common.c:(.text+0x1e0): undefined reference tomqtt_client_deinit' /usr/lib/gcc/x86_64-linux-gnu/7/../../../../lib/libiothub_client_mqtt_transport.a(iothubtransport_mqtt_common.c.o): In function publish_mqtt_telemetry_msg': iothubtransport_mqtt_common.c:(.text+0x1989): undefined reference tomqttmessage_create_in_place' iothubtransport_mqtt_common.c:(.text+0x1a63): undefined reference to mqtt_client_publish' iothubtransport_mqtt_common.c:(.text+0x1ad8): undefined reference tomqttmessage_destroy' /usr/lib/gcc/x86_64-linux-gnu/7/../../../../lib/libiothub_client_mqtt_transport.a(iothubtransport_mqtt_common.c.o): In function publish_device_method_message': iothubtransport_mqtt_common.c:(.text+0x1bc6): undefined reference tomqttmessage_create_in_place' iothubtransport_mqtt_common.c:(.text+0x1c32): undefined reference to mqtt_client_publish' iothubtransport_mqtt_common.c:(.text+0x1c93): undefined reference tomqttmessage_destroy' /usr/lib/gcc/x86_64-linux-gnu/7/../../../../lib/libiothub_client_mqtt_transport.a(iothubtransport_mqtt_common.c.o): In function publish_device_twin_get_message': iothubtransport_mqtt_common.c:(.text+0x1e65): undefined reference tomqttmessage_create' iothubtransport_mqtt_common.c:(.text+0x1ed4): undefined reference to mqtt_client_publish' iothubtransport_mqtt_common.c:(.text+0x1f52): undefined reference tomqttmessage_destroy'"

Here is the CMakelists.txt:

> cmake_minimum_required(VERSION 2.8.11)
set(AZUREIOT_INC_FOLDER ".." "/usr/include/azureiot")
include_directories(${AZUREIOT_INC_FOLDER})
set(my_c_files
        ./mqttsender.c
)

add_executable(mqttsender ${my_c_files})

target_link_libraries(mqttsender
        iothub_client
        iothub_client_mqtt_transport
        aziotsharedutil
        ssl
        pthread
        curl
        ssl
        crypto
        m
)

Here is the code:

#include <stdio.h>
#include <stdlib.h>
#include "iothub.h" //located at "/usr/include/azureiot/"
#include "iothubtransportmqtt.h" //for mqtt protocol types
#include "iothub_client.h"

int main()
{       int myrv;
        myrv = IoTHub_Init();
        char myconnectionstring[] = "blablablabla";
        printf("IoTHub_Init returns %d\n", myrv);
        if (IoTHubClient_LL_CreateFromConnectionString(myconnectionstring, MQTT_Protocol) == NULL)
        {
                (void)printf("ERROR: got no handle!\r\n");
        }
        else
        {
                (void)printf("INFORMATION: yeah, there is a handle!\n");
        }
        IoTHub_Deinit();
        printf("IoTHub_Deinit done.\n");
        return 0;
}

Thanks.

Answer 1

One step that helps was to add the parson library inside the CMakeLists.txt. Just added the line "parson" in the target_link_libraries section. Another step was to add the umqtt library inside the same section instead having nothing there resp. "uamqp" like in the example given here: https://github.com/Azure/azure-iot-sdk-c/blob/master/doc/ubuntu_apt-get_sample_setup.md#create-an-application-using-cmake

So now my CMakeLists.txt looks this way:

cmake_minimum_required(VERSION 2.8.11)
set(AZUREIOT_INC_FOLDER ".." "/usr/include/azureiot" "/usr/include/azureiot/inc")
include_directories(${AZUREIOT_INC_FOLDER})
set(my_c_files
        ./mqttsender.c
)

add_executable(mqttsender ${my_c_files})

target_link_libraries(mqttsender
        iothub_client
        iothub_client_mqtt_transport
        umqtt
        aziotsharedutil
        ssl
        pthread
        curl
        ssl
        crypto
        m
        parson
)

And my mqttclient can be compiled and is linked correctly :)

Hope that this will help somebody and sometimes.