+_rel/                         # 编译发布之后的目标文件. 
-bin/                         
cuttlefish
emqenv
emqttd
emqttd.cmd
emqttd_ctl
emqttd_ctl.cmd
install_upgrade_escript
nodetool
-data/                         
loaded_plugins               # 需要加载的插件放在这里.
+deps/                         # 所有依赖的app.
-rel/                          # 与发布相关的配置文件, 这些文件编译的时候大部分会被作为模板拷贝到目标文件中.
-conf/
-plugins/                  ## 插件的配置文件.
emq_dashboard.conf
acl.conf
emq.conf
-schema/
emq.schema
emq_dashboard.schema
erlang_vm.schema
.gitignore
LICENSE
Makefile                       # 和erlang.mk一起使用来编译和发布.
README.md
erlang.mk
relx                           # erlang release的程序.
relx.config                    # relx的配置文件.
vars.config                    # relx用于覆盖替换模板的文件.

init([]) ->
    {ok, {{rest_for_one, 10, 3600}, []}}.

start_link(Options, MFArgs, Logger) ->
    gen_server:start_link(?MODULE, [Options, MFArgs, Logger], []).

esockd_connection_sup.erl:

start_connection(Sup, Mod, Sock, SockFun) ->
    case call(Sup, {start_connection, Sock, SockFun}) of
        {ok, Pid, Conn} ->
                                                % transfer controlling from acceptor to connection
            Mod:controlling_process(Sock, Pid),
            Conn:go(Pid),
            {ok, Pid};
        {error, Error} ->
            {error, Error}
    end.

handle_call({start_connection, Sock, SockFun}, _From, 
            State = #state{conn_opts = ConnOpts, mfargs = MFArgs,
                           curr_clients = Count, access_rules = Rules}) ->
    case inet:peername(Sock) of
        {ok, {Addr, _Port}} ->
            case allowed(Addr, Rules) of
                true ->
                    Conn = esockd_connection:new(Sock, SockFun, ConnOpts),
                    case catch Conn:start_link(MFArgs) of
                        {ok, Pid} when is_pid(Pid) ->
                            ...

emqttd_client.erl:

start_link(Conn, Env) ->
    {ok, proc_lib:spawn_link(?MODULE, init, [[Conn, Env]])}.

init([Conn0, Env]) ->
    {ok, Conn} = Conn0:wait(),
    case Conn:peername() of
        {ok, Peername}    -> do_init(Conn, Env, Peername);
        {error, enotconn} -> Conn:fast_close(),
                             exit(normal);
        {error, Reason}   -> Conn:fast_close(),
                             exit({shutdown, Reason})
    end.

esockd_connection.erl:

wait(Conn = ?CONN_MOD) ->
    receive {go, Conn} -> upgrade(Conn) end.

handle_info({'EXIT', Pid, Reason}, State = #state{curr_clients = Count, logger = Logger}) ->
    ...

-type(trie_node_id() :: binary() | atom()).

%% 表示所有的节点，以及该节点的所有属性.
-record(trie_node,
        { node_id         :: trie_node_id(),
          edge_count = 0  :: non_neg_integer(),       %% edge_count表示这个节点是其他多少个节点的path。
          topic           :: binary() | undefined,    %% 该节点对应的完成topic.
          flags           :: [retained | static]
        }).
%% 表示一个node
-record(trie_edge,
        { node_id :: trie_node_id(),
          word    :: binary() | atom()
        }).

-record(trie,
        { edge    :: #trie_edge{},
          node_id :: trie_node_id()
        }).

> emqttd_topic:triples(<<"v2/a/+/c">>).
[{root,<<"v2">>,<<"v2">>},
 {<<"v2">>,<<"a">>,<<"v2/a">>},
 {<<"v2/a">>,'+',<<"v2/a/+">>},
 {<<"v2/a/+">>,<<"c">>,<<"v2/a/+/c">>}]