Example: comms_nodelets_example

Example output:

[publisher] Started
[subscriber] Connecting
[subscriber] Connected. Waiting for a message...
sub1: rx TPose3D[1.000000 2.000000 3.000000 11.459156 22.918312 34.377468]
sub2: rx TPose3D[1.000000 2.000000 3.000000 11.459156 22.918312 34.377468]
sub2: rx TPose3D[1.000000 2.000000 3.000000 11.459156 22.918312 34.377468]
onNewMsg2: idx=123 rx TPose3D[1.000000 2.000000 3.000000 11.459156 22.918312 34.377468]
sub1: rx TPose3D[1.000000 2.000000 3.000000 11.459156 22.918312 34.377468]
sub2: rx TPose3D[1.000000 2.000000 3.000000 11.459156 22.918312 34.377468]
sub2: rx TPose3D[1.000000 2.000000 3.000000 11.459156 22.918312 34.377468]
onNewMsg2: idx=123 rx TPose3D[1.000000 2.000000 3.000000 11.459156 22.918312 34.377468]
sub1: rx TPose3D[1.000000 2.000000 3.000000 11.459156 22.918312 34.377468]
sub2: rx TPose3D[1.000000 2.000000 3.000000 11.459156 22.918312 34.377468]
sub2: rx TPose3D[1.000000 2.000000 3.000000 11.459156 22.918312 34.377468]
onNewMsg2: idx=123 rx TPose3D[1.000000 2.000000 3.000000 11.459156 22.918312 34.377468]
sub1: rx TPose3D[1.000000 2.000000 3.000000 11.459156 22.918312 34.377468]
sub2: rx TPose3D[1.000000 2.000000 3.000000 11.459156 22.918312 34.377468]
sub2: rx TPose3D[1.000000 2.000000 3.000000 11.459156 22.918312 34.377468]
onNewMsg2: idx=123 rx TPose3D[1.000000 2.000000 3.000000 11.459156 22.918312 34.377468]
sub1: rx TPose3D[1.000000 2.000000 3.000000 11.459156 22.918312 34.377468]
sub2: rx TPose3D[1.000000 2.000000 3.000000 11.459156 22.918312 34.377468]
sub2: rx TPose3D[1.000000 2.000000 3.000000 11.459156 22.918312 34.377468]
onNewMsg2: idx=123 rx TPose3D[1.000000 2.000000 3.000000 11.459156 22.918312 34.377468]
[publisher] Finish

Contents of comms_nodelets_example/NodeletsTest_impl.cpp :

/* +------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)            |
   |                          https://www.mrpt.org/                         |
   |                                                                        |
   | Copyright (c) 2005-2022, Individual contributors, see AUTHORS file     |
   | See: https://www.mrpt.org/Authors - All rights reserved.               |
   | Released under BSD License. See: https://www.mrpt.org/License          |
   +------------------------------------------------------------------------+ */

#include <atomic>

std::atomic_bool nodelets_test_passed_ok = false;

#include <mrpt/comms/nodelets.h>
#include <mrpt/math/TPose3D.h>

#include <chrono>
#include <cstdio>  // printf()
#include <iostream>
#include <thread>

// Test payload:
const mrpt::math::TPose3D p_tx(1.0, 2.0, 3.0, 0.2, 0.4, 0.6);

// Create the topic directory. Only once per process, and must be shared
// by all nodelets/threads.
auto dir = mrpt::comms::TopicDirectory::create();

void thread_publisher()
{
    using namespace mrpt::comms;
    using namespace std;

    try
    {
#ifdef NODELETS_TEST_VERBOSE
        printf("[publisher] Started\n");
#endif

        for (int i = 0; i < 5; i++)
        {
            std::this_thread::sleep_for(100ms);
            dir->getTopic("/robot/odom")->publish(p_tx);
        }

#ifdef NODELETS_TEST_VERBOSE
        printf("[publisher] Finish\n");
#endif
    }
    catch (const std::exception& e)
    {
        cerr << e.what() << endl;
    }
    catch (...)
    {
        printf("[thread_publisher] Runtime error!\n");
    }
}

void onNewMsg(const mrpt::math::TPose3D& p)
{
#ifdef NODELETS_TEST_VERBOSE
    std::cout << "sub2: rx TPose3D" << p.asString() << std::endl;
#endif
}

void onNewMsg2(int idx, const mrpt::math::TPose3D& p)
{
#ifdef NODELETS_TEST_VERBOSE
    std::cout << "onNewMsg2: idx=" << idx << " rx TPose3D" << p.asString()
              << std::endl;
#endif
}

void thread_subscriber()
{
    using namespace mrpt::comms;
    using namespace std;

    try
    {
#ifdef NODELETS_TEST_VERBOSE
        printf("[subscriber] Connecting\n");
#endif

#ifdef NODELETS_TEST_VERBOSE
        printf("[subscriber] Connected. Waiting for a message...\n");
#endif

        // Create a subscriber with a lambda:
        Subscriber::Ptr sub1 =
            dir->getTopic("/robot/odom")
                ->createSubscriber<mrpt::math::TPose3D>(
                    [](const mrpt::math::TPose3D& p_rx) -> void {
#ifdef NODELETS_TEST_VERBOSE
                        std::cout << "sub1: rx TPose3D" << p_rx.asString()
                                  << std::endl;
#endif
                        nodelets_test_passed_ok = (p_rx == p_tx);
                    });

        // Create a subscriber with a regular function via std::function:
        auto sub2 =
            dir->getTopic("/robot/odom")
                ->createSubscriber<mrpt::math::TPose3D>(
                    std::function<void(const mrpt::math::TPose3D&)>(&onNewMsg));

        // Create a subscriber with a regular function:
        auto sub3 = dir->getTopic("/robot/odom")
                        ->createSubscriber<mrpt::math::TPose3D>(&onNewMsg);

        // Create a subscriber with std::bind:
        using namespace std::placeholders;
        auto sub4 = dir->getTopic("/robot/odom")
                        ->createSubscriber<mrpt::math::TPose3D>(
                            [](auto&& arg1) { return onNewMsg2(123, arg1); });

        // wait for messages to arrive.
        // The nodelet is up and live until "sub" gets out of scope.
        std::this_thread::sleep_for(2000ms);

#ifdef NODELETS_TEST_VERBOSE
        printf("[subscriber] Finish\n");
#endif
    }
    catch (const std::exception& e)
    {
        cerr << e.what() << endl;
    }
    catch (...)
    {
        cerr << "[thread_subscriber] Runtime error!" << endl;
    }
}

void NodeletsTest()
{
    using namespace std::chrono_literals;

    std::thread(thread_publisher).detach();
    std::thread(thread_subscriber).detach();
    std::this_thread::sleep_for(1000ms);
}

C++ example source code:

/* +------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)            |
   |                          https://www.mrpt.org/                         |
   |                                                                        |
   | Copyright (c) 2005-2022, Individual contributors, see AUTHORS file     |
   | See: https://www.mrpt.org/Authors - All rights reserved.               |
   | Released under BSD License. See: https://www.mrpt.org/License          |
   +------------------------------------------------------------------------+ */

#define NODELETS_TEST_VERBOSE
#include <mrpt/core/exceptions.h>

#include <iostream>

#include "NodeletsTest_impl.cpp"

int main()
{
    try
    {
        NodeletsTest();
        return 0;
    }
    catch (const std::exception& e)
    {
        std::cerr << "MRPT exception caught: " << e.what() << std::endl;
        return -1;
    }
}