net_kernel:monitor_nodes(Flag).%调用这个方法来订阅节点状态变动的消息.一个节点加入的时候会向所有的订阅进程发送一个nodeup消息,一个节点断开的时候会发送nodedown消息.  ```erlang  [net_kernel:disconnect(X) || X <- nodes() -- [List_of_wanted_nodes]]. net_kernel:allow(Nodes). net_kernel:monitor_nodes(true). init([]) -> ok = net_kernel:monitor_nodes(true), {ok, no_state}. handle_call(_Request, _From, State) -> {noreply, State}. handle_cast(_Msg, State) -> {noreply, State}. handle_info({nodeup, Node}, State) -> rabbit_log:info("node ~p up", [Node]), {noreply, State}; handle_info({nodedown, Node}, State) -> rabbit_log:info("node ~p down", [Node]), %% TODO: This may turn out to be a performance hog when there are %% lots of nodes. We really only need to execute this code on %%*one* node, rather than all of them. ok = rabbit_networking:on_node_down(Node), ok = rabbit_amqqueue:on_node_down(Node), {noreply, State}; net_kernel:start( [节点] ) net_kernel:stop(). net_kernel:disconnect(X) net_kernel:monitor_nodes(true). net_kernel:allow(Nodes). ```