tcp服务器和客户端交互

Posted 2023-03-15

【中文标题】tcp服务器和客户端交互

【英文标题】：tcp server and client interaction

【发布时间】：2016-07-28 22:16:11

【问题描述】：

我有一个 tcp 服务器（回显服务器）接受连接。我有一个客户端，当给定参数 N 时，它会创建许多试图与 tcp 侦听器连接的进程。我能够连接到这些套接字，但我可以看到许多套接字被关闭，这很明显，因为我使用的是回显服务器，我没有收到我发送的消息。

这是服务器代码（关键部分）

 init(State = #stateport = Port) ->
 ets:new(csockets, [ordered_set, named_table, public]),
 ets:insert(csockets, sockets, []),
 case gen_tcp:listen(Port, ?TCP_OPTIONS) of
   ok, LSocket ->
   NewState = State#statelsocket = LSocket,
   spawn(fun() -> accept(NewState) end),
   ok, NewState;
   error, Reason ->
    stop, Reason
  end.


  accept(State = #statelsocket = LSocket) ->
  case gen_tcp:accept(LSocket) of
   ok, Socket ->
   sockets, List = hd(ets:lookup(csockets, sockets)),
   NewList = [Socket | List],
   ets:insert(csockets, sockets, NewList),
   Pid = spawn(fun() ->
    loop(Socket)
              end),
    gen_tcp:controlling_process(Socket, Pid),
    accept(State);
    error, closed -> State
    end.


   loop(Socket) ->
   case gen_tcp:recv(Socket, 0) of
   ok, Data ->
   gen_tcp:send(Socket, Data),
   loop(Socket);
    error, closed ->
    io:format("CLOSED ~n"),  %% This asserts for many sockets
    ok
    end.

连接到服务器的客户端。创建 N 个进程连接到服务器，然后使用返回的套接字进行通信。

     send(State = #state) ->
     Low = State#state.low,
     High = State#state.high + 1,
     case Low of
      High -> State;
      _Else ->
      N = Low rem 10,
      Dest = lists:nth(1, State#state.dest),
      spawn(?MODULE, loop, [Dest, Low]),
      NewState = State#statelow = Low + 1,
       send(NewState)
      end.

      loop(IP, Port, Low) ->
      case gen_tcp:connect(IP, Port, [binary, active, true]) of
      ok, Socket ->
       io:format("~p Connected ~n", [Low]),
       gen_tcp:send(Socket, "Hi"),
      receive
       tcp, RecPort, Data ->
       io:format("I have received ~p on port ~p ~n", [Data, RecPort])
      end;
      _Else ->
      io:format("The connection failed ~n")
      loop(IP, Port, Low)
      end.

【参考方案1】：

错误出现在您的服务器上，您正在与关闭的 tcp 上的类似消息进行模式匹配：

error, closed 

但是如果您查看gen_tcp 的文档，您会注意到您应该对这些消息进行模式匹配：

tcp_closed, Socket
tcp_error, Socket, Reason

更新您的代码：

loop(Socket) ->
    case gen_tcp:recv(Socket, 0) of
        ok, Data ->
            gen_tcp:send(Socket, Data),
            loop(Socket);
        tcp_error, Socket ->
            io:format("CLOSED ~n"),  %% This asserts for many sockets
            ok
    end.

您应该开始在屏幕上显示 CLOSED 字符串