判断订阅时的连接状态(目前不能区分多个设备)

1. 增加普通变量，名为substate

2.生成变量变化函数

3. 判断连接成功

void HmiApp::v28_tri_cb(uint16_t code, LvEvent e) {
    //变量[substate]值变化触发函数
    int v;
    vm->getInt("substate", v);
    cout<<"mqtt status:"<<v<<endl;
    if(v == 0) {
        cout<< "connect ok." <<endl;
    }
}

4.状态说明

0：连接成功

100：开始mqtt线程

101：开始尝试订阅

105：没有设置主题、服务器或端口

其他

    MOSQ_ERR_AUTH_CONTINUE = -4,
    MOSQ_ERR_NO_SUBSCRIBERS = -3,
    MOSQ_ERR_SUB_EXISTS = -2,
    MOSQ_ERR_CONN_PENDING = -1,
    MOSQ_ERR_SUCCESS = 0,
    MOSQ_ERR_NOMEM = 1,
    MOSQ_ERR_PROTOCOL = 2,
    MOSQ_ERR_INVAL = 3,
    MOSQ_ERR_NO_CONN = 4,
    MOSQ_ERR_CONN_REFUSED = 5,
    MOSQ_ERR_NOT_FOUND = 6,
    MOSQ_ERR_CONN_LOST = 7,
    MOSQ_ERR_TLS = 8,
    MOSQ_ERR_PAYLOAD_SIZE = 9,
    MOSQ_ERR_NOT_SUPPORTED = 10,
    MOSQ_ERR_AUTH = 11,
    MOSQ_ERR_ACL_DENIED = 12,
    MOSQ_ERR_UNKNOWN = 13,
    MOSQ_ERR_ERRNO = 14,
    MOSQ_ERR_EAI = 15,
    MOSQ_ERR_PROXY = 16,
    MOSQ_ERR_PLUGIN_DEFER = 17,
    MOSQ_ERR_MALFORMED_UTF8 = 18,
    MOSQ_ERR_KEEPALIVE = 19,
    MOSQ_ERR_LOOKUP = 20,
    MOSQ_ERR_MALFORMED_PACKET = 21,
    MOSQ_ERR_DUPLICATE_PROPERTY = 22,
    MOSQ_ERR_TLS_HANDSHAKE = 23,
    MOSQ_ERR_QOS_NOT_SUPPORTED = 24,
    MOSQ_ERR_OVERSIZE_PACKET = 25,
    MOSQ_ERR_OCSP = 26,
    MOSQ_ERR_TIMEOUT = 27,
    MOSQ_ERR_RETAIN_NOT_SUPPORTED = 28,
    MOSQ_ERR_TOPIC_ALIAS_INVALID = 29,
    MOSQ_ERR_ADMINISTRATIVE_ACTION = 30,
    MOSQ_ERR_ALREADY_EXISTS = 31,