什么是DCPS，它与DDS有什么关系？

DCPS是一种分布式消息传递协议，用于DDS（数据分发服务）中的通信。DDS是一种分布式数据传输系统，用于跨网络连接和传输数据。DDS使用DCPS协议以异步和可靠的方式进行数据传输。以下是使用DDS和DCPS进行数据传输的示例代码：

#include <ndds/ndds_cpp.h>

// Define a structure for the data to be transmitted
struct SensorData
{
    char* sensorName;
    float value;
};

int main(int argc, char *argv[])
{
    // Create an instance of the DomainParticipant factory
    DDSDomainParticipantFactory* factory = DDSDomainParticipantFactory::get_instance();

    // Create a DomainParticipant
    DDSDomainParticipant* participant = factory->create_participant(0, DDS_PARTICIPANT_QOS_DEFAULT, NULL, DDS_STATUS_MASK_NONE);
    
    // Create a Topic
    DDS_Topic* topic = participant->create_topic("SensorData", 
                                                  SensorDataTypeSupport::get_type_name(),
                                                  DDS_TOPIC_QOS_DEFAULT, NULL, DDS_STATUS_MASK_NONE);

    // Create a Publisher
    DDSPublisher* publisher = participant->create_publisher(DDS_PUBLISHER_QOS_DEFAULT, NULL, DDS_STATUS_MASK_NONE);
    
    // Create a DataWriter
    DDSDataWriter* writer = publisher->create_datawriter(topic, DDS_DATAWRITER_QOS_DEFAULT, NULL, DDS_STATUS_MASK_NONE);

    // Serialize and transmit the sensor data
    SensorData data;
    data.sensorName = "Temperature Sensor";
    data.value = 75.5;
    SensorDataDataWriter* sensorDataWriter = SensorDataDataWriter::narrow(writer);
    sensorDataWriter->write(data, DDS_HANDLE_NIL);

    // Cleanup
    participant->delete_contained_entities();
    factory->delete_participant(participant);
    DDSDomainParticipantFactory::finalize();
    return 0;
}