Mosquitto创建MQTT服务器提示Starting in local only mode的解决办法

一、问题现象

使用新下载的Mosquitto创建MQTT服务器提示Starting in local only mode. Connections will only be possible from clients running on this machine.测试发现服务器只能接入本机的客户端，而其他设备上的客户端在连接时直接被重置了。

二、原因分析

随后查阅了一下Mosquitto的更新记录，原来在其2.0.0大版本更新后如果不加载配件文件则使用回环接口（仅可用于本地Socket通信）。

Breaking changes

• When the Mosquitto broker is run without configuring any listeners it will now bind to the loopback interfaces 127.0.0.1 and/or ::1. This means that only connections from the local host will be possible.

Running the broker as mosquitto or mosquitto -p 1883 will bind to the loopback interface.

Running the broker with a configuration file with no listeners configured will bind to the loopback interface with port 1883.

Running the broker with a listener defined will bind by default to 0.0.0.0 / :: and so will be accessible from any interface. It is still possible to bind to a specific address/interface.

Mosquitto更新记录: https://mosquitto.org/blog/2020/12/version-2-0-0-released

三、解决方法

先修改软件安装目录中的配置文件mosquitto.conf然后加载配置文件来启动服务器。

1. 配置端口号，编辑mosquitto.conf，搜索listener去掉行首的#并加上端口号，示例端口为1883

   # On systems that support Unix Domain Sockets, it is also possible
   # to create a # Unix socket rather than opening a TCP socket. In
   # this case, the port number should be set to 0 and a unix socket
   # path must be provided, e.g.
   # listener 0 /tmp/mosquitto.sock
   #
   # listener port-number [ip address/host name/unix socket path]

   listener 1883

2. 启用匿名访问，若不允许匿名访问则只有添加客户端鉴权信息才能接入。为简化测试我们启用匿名访问：将mosquitto.conf里的allow_anonymous选项改为true并保存

   # Boolean value that determines whether clients that connect
   # without providing a username are allowed to connect. If set to
   # false then a password file should be created (see the
   # password_file option) to control authenticated client access.
   #
   # Defaults to false, unless there are no listeners defined in the configuration
   # file, in which case it is set to true, but connections are only allowed from
   # the local machine.
   allow_anonymous true

3. 加载配置文件启动服务器测试，执行命令mosquitto.exe -c mosquitto.conf -v，此时LOG上已经没了Starting in local only mode且非本地客户端可以正常接入了