我正在使用Paho MQTT客户端与本地客户端进行小型IoT项目，将mqtt数据发送到本地mosquitto代理（充当网桥），然后发送到我的远程代理（SAP IoT Cloud）。
从客户端到远程代理的数据流（使用TLS）已成功运行，现在我正努力在相应位置之间放置和配置桥接器。
由于我必须对mqtt消息（QoS 1）使用TLS，所以将创建另一个具有端口8883的侦听器。还提供与用于发送的客户端相同的CA文件，用于与远程代理进行身份验证。一旦使用下面所述的配置启动经纪人（我还没有启动本地客户端），我将收到不可接受的协议版本的错误消息（请参见下面的日志文件）。因此无法建立到我的远程代理的桥接连接，但是为什么呢？
我以前遇到过同样的问题，然后发现我使用的是旧的mosquitto版本（1.4.10），并进行了相应的更新。但是，对于v1.6.7来说，它也不起作用。
任何提示都非常感谢。一些信息已取消个性化设置（例如在远程代理中用作clientId的连接名称，端点地址）
一些必要的信息：
connection raspberryPiZero
address xxxxxxxx.eu10.cp.iot.sap:8883
topic # both 1
log_type all
listener 8883
bridge_cafile /etc/mosquitto/certs/CAcert.pem
1574754457: mosquitto version 1.6.7 starting
1574754457: Config loaded from /etc/mosquitto/mosquitto.conf.
1574754457: Opening ipv4 listen socket on port 1883.
1574754457: Opening ipv6 listen socket on port 1883.
1574754715: mosquitto version 1.6.7 terminating
1574754715: Saving in-memory database to /var/lib/mosquitto/mosquitto.db.
1574754721: mosquitto version 1.6.7 starting
1574754721: Config loaded from /etc/mosquitto/mosquitto.conf.
1574754721: Opening ipv4 listen socket on port 8883.
1574754721: Opening ipv6 listen socket on port 8883.
1574754721: Bridge local.raspberrypi.raspberryPiZero doing local SUBSCRIBE on topic #
1574754721: Connecting bridge (step 1) raspberryPiZero (xxxxxxxx.eu10.cp.iot.sap:8883)
1574754726: Bridge local.raspberrypi.raspberryPiZero doing local SUBSCRIBE on topic #
1574754726: Connecting bridge (step 1) raspberryPiZero (xxxxxxxx.eu10.cp.iot.sap:8883)
1574754741: Bridge local.raspberrypi.raspberryPiZero doing local SUBSCRIBE on topic #
1574754741: Connecting bridge (step 1) raspberryPiZero (xxxxxxxx.eu10.cp.iot.sap:8883)
1574754741: Connecting bridge (step 2) raspberryPiZero (xxxxxxxx.eu10.cp.iot.sap:8883)
1574754741: Bridge raspberrypi.raspberryPiZero sending CONNECT
1574754742: Received CONNACK on connection local.raspberrypi.raspberryPiZero.
1574754742: Connection Refused: unacceptable protocol version
1574754742: Socket error on client local.raspberrypi.raspberryPiZero, disconnecting.
1574754747: Bridge local.raspberrypi.raspberryPiZero doing local SUBSCRIBE on topic #
1574754747: Connecting bridge (step 1) raspberryPiZero (xxxxxxxx.eu10.cp.iot.sap:8883)
1574754747: Connecting bridge (step 2) raspberryPiZero (xxxxxxxx.eu10.cp.iot.sap:8883)
1574754747: Bridge raspberrypi.raspberryPiZero sending CONNECT
1574754747: Received CONNACK on connection local.raspberrypi.raspberryPiZero.
1574754747: Connection Refused: broker unavailable
1574754747: Socket error on client local.raspberrypi.raspberryPiZero, disconnecting.
1574754775: Bridge local.raspberrypi.raspberryPiZero doing local SUBSCRIBE on topic #
1574754775: Connecting bridge (step 1) raspberryPiZero (xxxxxxxx.eu10.cp.iot.sap:8883)
1574754776: Connecting bridge (step 2) raspberryPiZero (xxxxxxxx.eu10.cp.iot.sap:8883)
1574754776: Bridge raspberrypi.raspberryPiZero sending CONNECT
1574754776: Received CONNACK on connection local.raspberrypi.raspberryPiZero.
1574754776: Connection Refused: broker unavailable
1574754776: Socket error on client local.raspberrypi.raspberryPiZero, disconnecting.
1574754781: Bridge local.raspberrypi.raspberryPiZero doing local SUBSCRIBE on topic #
1574754781: Connecting bridge (step 1) raspberryPiZero (xxxxxxxx.eu10.cp.iot.sap:8883)
1574754782: Connecting bridge (step 2) raspberryPiZero (xxxxxxxx.eu10.cp.iot.sap:8883)
1574754782: Bridge raspberrypi.raspberryPiZero sending CONNECT
1574754782: Received CONNACK on connection local.raspberrypi.raspberryPiZero.
1574754782: Connection Refused: broker unavailable
1574754782: Socket error on client local.raspberrypi.raspberryPiZero, disconnecting.
1574754787: Bridge local.raspberrypi.raspberryPiZero doing local SUBSCRIBE on topic #
1574754787: Connecting bridge (step 1) raspberryPiZero (xxxxxxxx.eu10.cp.iot.sap:8883)
1574754788: Connecting bridge (step 2) raspberryPiZero (xxxxxxxx.eu10.cp.iot.sap:8883)
1574754788: Bridge raspberrypi.raspberryPiZero sending CONNECT
1574754788: Received CONNACK on connection local.raspberrypi.raspberryPiZero.
1574754788: Connection Refused: broker unavailable
1574754788: Socket error on client local.raspberrypi.raspberryPiZero, disconnecting.
1574754793: Bridge local.raspberrypi.raspberryPiZero doing local SUBSCRIBE on topic #
1574754793: Connecting bridge (step 1) raspberryPiZero (xxxxxxxx.eu10.cp.iot.sap:8883)
1574754794: Connecting bridge (step 2) raspberryPiZero (xxxxxxxx.eu10.cp.iot.sap:8883)
1574754794: Bridge raspberrypi.raspberryPiZero sending CONNECT
1574754794: Received CONNACK on connection local.raspberrypi.raspberryPiZero.
1574754794: Connection Refused: broker unavailable
1574754794: Socket error on client local.raspberrypi.raspberryPiZero, disconnecting.
1574754799: Bridge local.raspberrypi.raspberryPiZero doing local SUBSCRIBE on topic #
1574754799: Connecting bridge (step 1) raspberryPiZero (xxxxxxxx.eu10.cp.iot.sap:8883)
1574754800: Connecting bridge (step 2) raspberryPiZero (xxxxxxxx.eu10.cp.iot.sap:8883)
1574754800: Bridge raspberrypi.raspberryPiZero sending CONNECT
1574754800: Received CONNACK on connection local.raspberrypi.raspberryPiZero.
1574754800: Connection Refused: broker unavailable
1574754800: Socket error on client local.raspberrypi.raspberryPiZero, disconnecting.
1574754805: Bridge local.raspberrypi.raspberryPiZero doing local SUBSCRIBE on topic #
1574754805: Connecting bridge (step 1) raspberryPiZero (xxxxxxxx.eu10.cp.iot.sap:8883)
1574754806: Connecting bridge (step 2) raspberryPiZero (xxxxxxxx.eu10.cp.iot.sap:8883)
1574754806: Bridge raspberrypi.raspberryPiZero sending CONNECT
1574754806: Received CONNACK on connection local.raspberrypi.raspberryPiZero.
1574754806: Connection Refused: broker unavailable
1574754806: Socket error on client local.raspberrypi.raspberryPiZero, disconnecting.
1574754811: Bridge local.raspberrypi.raspberryPiZero doing local SUBSCRIBE on topic #
1574754811: Connecting bridge (step 1) raspberryPiZero (xxxxxxxx.eu10.cp.iot.sap:8883)
1574754812: Connecting bridge (step 2) raspberryPiZero (xxxxxxxx.eu10.cp.iot.sap:8883)
1574754812: mosquitto version 1.6.7 terminating
1574754812: Saving in-memory database to /var/lib/mosquitto/mosquitto.db.
默认情况下，蚊子试图使用MQTT 3.1建立网桥
您可以通过将bridge_protocol_version选项添加到它接受mqttv31和mqttv311的网桥配置中来进行更改
bridge_protocol_version mqttv311
尝试使用3.11
也通过以下方式禁用mosquitto专用网桥扩展：
try_private false