sockets - erlang套接字(使用牧场)在短时间内关闭？

Question

我用ranch监听socket，但是在短短的五秒左右，ranch关闭了socket，我的socket设置就在上面了，怎么回事？

    {ok, _} = ranch:start_listener(server,200, ranch_tcp, [{port, 5555},{active, once},    {max_connections, 1024}], server_protocol, []), %% start the listener

协议(protocol)文件在下面，牧场监听接受一个套接字，并反向接收数据，但问题是，当向客户端发送数据时，大约五秒钟后，客户端收到消息说套接字是被服务器关闭了，我不知道是不是牧场的默认设置导致了这个？

-module(reverse_protocol).
-behaviour(gen_server).
-behaviour(ranch_protocol).
%% API.
-export([start_link/4]).
%% gen_server.
-export([init/1]).
-export([init/4]).
-export([handle_call/3]).
-export([handle_cast/2]).
-export([handle_info/2]).
-export([terminate/2]).
-export([code_change/3]).
-define(TIMEOUT, 5000).
-record(state, {socket, transport}).

%% API.
start_link(Ref, Socket, Transport, Opts) ->
proc_lib:start_link(?MODULE, init, [Ref, Socket, Transport, Opts]).
%% gen_server.
%% This function is never called. We only define it so that
%% we can use the -behaviour(gen_server) attribute.

init([]) -> {ok, undefined}.

init(Ref, Socket, Transport, _Opts = []) ->
ok = proc_lib:init_ack({ok, self()}),
ok = ranch:accept_ack(Ref),
ok = Transport:setopts(Socket, [{active, once}]),
gen_server:enter_loop(?MODULE, [],
    #state{socket=Socket, transport=Transport},
    ?TIMEOUT).

handle_info({tcp, Socket, Data}, State=#state{
    socket=Socket, transport=Transport}) ->
Transport:setopts(Socket, [{active, once}]),
Transport:send(Socket, reverse_binary(Data)),
{noreply, State, ?TIMEOUT};

handle_info({tcp_closed, _Socket}, State) ->
{stop, normal, State};

handle_info({tcp_error, _, Reason}, State) ->
{stop, Reason, State};

handle_info(timeout, State) ->
{stop, normal, State};

handle_info(_Info, State) ->
{stop, normal, State}.

handle_call(_Request, _From, State) ->
{reply, ok, State}.

handle_cast(_Msg, State) ->
{noreply, State}.

terminate(_Reason, _State) ->
ok.

code_change(_OldVsn, State, _Extra) ->
{ok, State}.

%% Internal.
reverse_binary(B) when is_binary(B) ->
[list_to_binary(lists:reverse(binary_to_list(
    binary:part(B, {0, byte_size(B)-2})
))), "\r\n"].

Answer 1

所以你的问题是因为你的 gen_server 进程超时并关闭。关闭的套接字是这样做的副作用，因为牧场将套接字链接到生成的处理程序进程。

一旦新进程进入 gen_server 循环并调用 gen_server:enter_loop , 它有 ?TIMEOUT在发送消息之前接收消息的毫秒数 timeout信息。

-define(TIMEOUT, 5000).

init(Ref, Socket, Transport, _Opts = []) ->
  ok = proc_lib:init_ack({ok, self()}),
  ok = ranch:accept_ack(Ref),
  ok = Transport:setopts(Socket, [{active, once}]),
  gen_server:enter_loop(?MODULE, [],
    #state{socket=Socket, transport=Transport},
    ?TIMEOUT). %% timeout because of this!

handle_info({tcp, Socket, Data}, State=#state{
  socket=Socket, transport=Transport}) ->
  Transport:setopts(Socket, [{active, once}]),
  Transport:send(Socket, reverse_binary(Data)),
  {noreply, State, ?TIMEOUT}; %% timeout because of this!

因此，当这五秒钟过去并且 gen_server 在那段时间内没有收到任何消息时，它会向自己发送一个 timeout消息，然后由 handle_info 处理

handle_info(timeout, State) ->
  {stop, normal, State};

您的 handle_info告诉 gen_server 停止，这会导致 Socket 关闭，因为两者是链接在一起的。

您可以完全删除超时，或者只是阻止超时导致进程关闭。

这是我将如何更改 handle_info超时代码:

handle_info(timeout, State) ->
  io:format("the socket is idle~n"),
  {noreply,State};