erlang并行服务器错误？

我决定修改中的代码，将服务器更改为并行服务器（如本书中所述），但它无法正常工作。根据《编程Erlang》一书，下面的代码应该是presto chango，但我在第17行遇到了一个错误。这是并行服务器代码（完成的并行服务器位于底部，这只是对最后一个线程上的旧服务器代码的更改）

这就是错误所在

=ERROR REPORT==== 12-Feb-2013::23:05:13 ===
Error in process <0.35.0> with exit value: {{badmatch,{error,einval}},[{ps1,loop,1,[{file,"ps1.erl"},{line,17}]}]}

接下来是客户端代码，它也会在等待回复时死去

c1:nano("list_to_tuple([2+3*4,10+20])").
nano got not answer to "list_to_tuple([2+3*4,10+20])"
{error,timeout}

-module(c1).
-compile(export_all).
-import(lists, [reverse/1]).

%old port 2345
nano(Str) ->
    {ok, Socket} = 
    gen_tcp:connect("localhost", 4042,
            [binary, {packet, 0}]),
    ok = gen_tcp:send(Socket, term_to_binary(Str)),
    R = receive
        {tcp,Socket,Bin} ->
            io:format("Client received binary = ~p~n",[Bin]),
            Val = binary_to_term(Bin),
            io:format("Client result = ~p~n",[Val]),
            {ok,Val}
        after 5000 ->
            io:format("nano got no answer to ~p~n",[Str]),
            {error,timeout}
    end,
%   gen_tcp:close(Socket),
    R.

---

根据文档，您得到的错误描述有点奇怪：

埃因瓦尔

Attempt to delete the current directory. On some platforms, eacces is returned instead.

我必须说，这没有多大帮助

无论如何，您不需要在循环中调用

{ok，Socket}=gen\u tcp:accept（Listen）

，而它已经在

par\u connect（Listen）

中完成了。但是在这种情况下，循环的参数将是Socket而不是Listen。您在per_connect中进行了更正，但没有在loop中进行更正（这是您得到错误的原因）

执行此操作时，第一个服务器是spawn，它初始化与gen_tcp:listen的连接，并等待与gen_tcp:accept的连接。一旦建立了连接，就会启动一个新进程，等待接受，并在当前进程中调用循环，连接端口作为参数

现在，您应该编写一个比我建议的更智能的客户端，它可以使用相同的开放连接循环一段时间：o）

---

请发布用于测试客户端和服务器的命令，好吗？谢谢…我开始3个虚拟机：werl-sname w0，werl-sname w1和werl-sname w2。在一个VM中，我启动服务器：socket\u示例：start\u nano\u server（），在另一个VM中，我启动客户机socket\u示例：nano\u client\u eval（“来自w1的你好”）。和socket_示例：nano_client_eval（“来自w2的你好”）。一个客户端可以在服务器窗口中启动，但我更喜欢在不同的窗口中分离不同的打印输出。

c1:nano("list_to_tuple([2+3*4,10+20])").
nano got not answer to "list_to_tuple([2+3*4,10+20])"
{error,timeout}

-module(c1).
-compile(export_all).
-import(lists, [reverse/1]).

%old port 2345
nano(Str) ->
    {ok, Socket} = 
    gen_tcp:connect("localhost", 4042,
            [binary, {packet, 0}]),
    ok = gen_tcp:send(Socket, term_to_binary(Str)),
    R = receive
        {tcp,Socket,Bin} ->
            io:format("Client received binary = ~p~n",[Bin]),
            Val = binary_to_term(Bin),
            io:format("Client result = ~p~n",[Val]),
            {ok,Val}
        after 5000 ->
            io:format("nano got no answer to ~p~n",[Str]),
            {error,timeout}
    end,
%   gen_tcp:close(Socket),
    R.

Attempt to delete the current directory. On some platforms, eacces is returned instead.

-module(socket_examples).
-compile(export_all).

nano_client_eval(Str) ->
    {ok, Socket} = gen_tcp:connect("localhost", 2345,[binary, {packet, 0}]),
    nano_client_eval(Str,10,Socket).

nano_client_eval(_,0,Socket) ->
    gen_tcp:close(Socket);
nano_client_eval(Str,N,Socket) ->
    ok = gen_tcp:send(Socket, term_to_binary(Str ++ " loop " ++ integer_to_list(N))),
    receive
        {tcp,Socket,Bin} ->
            io:format("Client received binary = ~p on socket ~p~n",[Bin,Socket]),
            Val = binary_to_term(Bin),
            io:format("Client result = ~p~n",[Val]),
            timer:sleep(1000),
            nano_client_eval(Str,N-1,Socket)
        after 5000 ->
            io:format("nano_client_eval got not answer to ~p~n",[Str]),
            {error,timeout}
    end.

start_nano_server() ->
    {ok, Listen} = gen_tcp:listen(2345, [binary, {packet, 0},{reuseaddr, true},{active, true}]),                       
    spawn(fun() -> par_connect(Listen) end).

par_connect(Listen) ->      
    {ok, Socket} = gen_tcp:accept(Listen),
    spawn(fun() -> par_connect(Listen) end),
    loop(Socket).                    

loop(Socket) ->
    receive
    {tcp, Socket, Bin} ->
        io:format("Server received binary = ~p~n",[Bin]),
        Str = binary_to_term(Bin),  %% (9)
        io:format("Server (unpacked)  ~p~n",[Str]),
%        Reply = lib_misc:string2value(Str),  %% (10)
        Reply = string:to_upper(Str),  %% (10)
        io:format("Server replying = ~p~n",[Reply]),
        gen_tcp:send(Socket, term_to_binary(Reply)),  %% (11)
        loop(Socket);
    {tcp_closed, Socket} ->
            io:format("Server socket ~p closed by request~n",[Socket])
    after 60000 ->
            gen_tcp:close(Socket),
            io:format("Server socket ~p closed, no more activity~n",[Socket])
    end.