Question

我在不同线程中运行各种mqtt客户端并与代理通信客户端。我还以不同线程的形式模拟传感器数据，并在随机时间（通常以毫秒或几秒）触发它们。我发布了我面临问题的下面的代码。问题是有效负载消息并不总是被访问（订阅的消息数据）。有效载荷在复制到字符串时显示为空白。

       {
           std::lock_guard<std::mutex> l(sub_mtx);
           msg_strm<<(char *) message->payload;
           sub_msg=msg_strm.str();
      }
    std::cout<<sub_msg<<std::endl;

//}

int remaining_lngth;

if(message->qos !=0){
    std::cout<<"QOS IS NOT ZERO HERE"<<std::endl;
    remaining_lngth=2+topicLen+2+message->payloadlen;
} else{
    remaining_lngth=2+topicLen+message->payloadlen;
}

//   std::cout<<"YOUR PAYLOAD SUBSCRIBED IS"<< sub_msg<<std::endl;
{
    std::lock_guard<std::mutex> l(sub_mtx);
    std::cout << "PUBLISH MESSAGE LENGTH IS" << message->payloadlen << std::endl;
    sub_dmp_pkt_strm << "Message Type :  8" << "\n";
    sub_dmp_pkt_strm << "Duplicate Flag :" << message->dup << "\n";
    sub_dmp_pkt_strm << "QoS Level : " << message->qos << "\n";
    sub_dmp_pkt_strm << "RETAIN Flag : " << message->retained << "\n";
    sub_dmp_pkt_strm << "Remaining Length :" << remaining_lngth << "\n";
    sub_dmp_pkt_strm << "Topic Name String Length (MSB) : 0 " << "\n";
    sub_dmp_pkt_strm << "Topic Name String Length (LSB) : " << topicLen << "\n";
    sub_dmp_pkt_strm << "Topic Name : " << topicName << "\n";
    sub_dmp_pkt_strm << "Message ID (MSB) : " << message->msgid << "\n";
    sub_dmp_pkt_strm << "Message ID (LSB) : 0 " << "\n";
    sub_dmp_pkt_strm << "Publish Message : " + sub_msg + "\n";
    sub_dmp_pkt = sub_dmp_pkt_strm.str();
    log_packet_event(clnt_id, "SUBSCRIBE", sub_dmp_pkt.c_str(), remaining_lngth);
}

然后我将整个数据包格式写入数据库。

无法从paho客户端获取订阅的有效负载的值

0 个答案: