本帖最后由 xmlhttp 于 2019-5-9 21:07 编辑

直接拿的LWIP扩展例程的网络实验8 NETCONN_TCP客户端这个修改的，连接服务器代码如下：
[mw_shl_code=applescript,true]
u8 mqtt_connect(void)
{
    MQTTPacket_connectData data = MQTTPacket_connectData_initializer;
    unsigned char buf[200];
    int buflen = sizeof(buf);
    int len = 0;
    memset(buf,'',buflen);
    data.clientID.cstring = "STM32F103_TEST";
    data.keepAliveInterval = 20;     
    data.cleansession =0;
    data.username.cstring = "m1";
    data.password.cstring = "admin";
    data.MQTTVersion = 4;
    len = MQTTSerialize_connect(buf, buflen, &data);
    transport_sendPacketBuffer((char*)buf,len);
    delay_ms(100);
    if (MQTTPacket_read(buf, buflen, transport_getdata) == CONNACK)
    {
        unsigned char sessionPresent, connack_rc;
       if ( MQTTDeserialize_connack(&sessionPresent, &connack_rc, buf, buflen)!= 1 || connack_rc != 0)
        {
            printf("Unable to connect, return code %d ", connack_rc);
            return 0;
        }
        else
        {
            printf("MQTT CONNECT! ");
        }
    }
    else
        printf("No connack ");
        return 0;
}
[/mw_shl_code]
在服务端有这样的日志输出：
1557404053: New client connected from x.x.x.x as STM32F103_TEST (p2, c0, k20, u'm1').
1557404053: No will message specified.
1557404053: Sending CONNACK to STM32F103_TEST (1, 0)

运行到MQTTDeserialize_connack(&sessionPresent, &connack_rc, buf, buflen)等于1，connack_rc=2
串口中打印 Unable to connect, return code 2，请问要怎么修改？