Question

我正在Erlang中开发一个简单的框架来处理2人回合制游戏。代码如下：

-module(game).
-export([start_server/0,generate_server/0,add_player/0,remove_player/0]).


generate_server() ->
Table_num = 0,
Player_num = 0,
io:format("Server generated...~n", []),
io:format("The current number of tables is ~w~n", [Table_num]),
io:format("The current number of players is ~w~n", [Player_num]),
receive
    login ->
        io:format("A new player has connected!~n", []),
        New = Player_num + 1,
        io:format("The current number of players is ~w~n", [New]);
    logout ->
        io:format("You have beeen succesfully disconnected~n", [])
end.



start_server() ->
    io:format("Welcome player!~nInitializing game...~n", []),
    io:format("Generating server...~n", []),
    register(server,spawn(game, generate_server, [])).


add_player() ->
    server ! login.


remove_player() ->
    server ! logout.

运行此代码时存在两个主要问题：

当我执行add_player（）然后执行remove_player（）时，第二个函数崩溃并出现异常
如果我在一个终端窗口上启动程序，然后在第二个终端窗口上执行add_player（），则会出错。如何才能在多个终端窗口上运行它？

任何帮助都将受到高度赞赏。

Answer 1

1 / 您的服务器中没有循环。当你启动它时，在一些打印之后，它会等待接收语句。

当收到登录消息时，它执行操作，然后服务器代码完成;该过程死亡并且未注册。所有变量都会消失，VM会清理内存......

因此，稍后，任何向服务器发送消息的进程都将崩溃，因为您使用的是不再注册的名称。

要使其正常工作，您应该保留已连接的播放器列表（例如列表中）并使用此列表作为参数调用服务器循环。

generate_server(Tlist,Plist) ->
io:format("The current number of tables is ~w~n", [length(Tlist)]),
io:format("The current number of players is ~w~n", [length(Plist)]),
receive
    {login,Name} ->
        io:format("A new player ~p has connected!~n", [Name]),
        generate_server(Tlist,[Name|Plist]);
    {logout,Name} ->
        io:format("You have beeen succesfully disconnected~n", []),
        generate_server(Tlist,lists:delete(Name,Plist))
end.

，对generate_server的调用由

完成

register(server,spawn(game, generate_server, [[],[]]))

2 / 为了在2个不同的节点之间使用erlang消息，您需要：

分享同样的erlang coockie
发现节点（例如使用netadm）
获取服务器pid或使用golbal注册名称

参见http://learnyousomeerlang.com/distribunomicon#alone-in-the-dark

的示例

Answer 2

您错过了服务器的loop正文。您的程序崩溃，因为服务器只收到一条消息并退出。考虑以下服务器的另一个版本：

generate_server() ->
    Table_num = 0,
    Player_num = 0,
    io:format("Server generated...~n", []),
    io:format("The current number of tables is ~w~n", [Table_num]),
    io:format("The current number of players is ~w~n", [Player_num]),
    loop([]).

loop(Players)->
    receive
        {From,{login,PlayerId}} ->
            io:format("A new player has connected!~n", []),
            io:format("The current number of players is ~w~n", [New]),
            NewPlayers = case lists:member(PlayerId,Players) of
                            true ->
                                From ! {login_failed,exists},
                                Players;
                            false -> 
                                From ! {login_success,true},
                                [PlayerId|Players]
                        end,
            loop(NewPlayers);
        {From,{logout,PlayerId}} ->
            NewPlayers = case lists:member(PlayerId,Players) of
                            true ->
                                From ! {logout,ok},
                                Players -- [PlayerId];
                            false -> 
                                From ! {logout,failed},
                                Players
                        end,
            loop(NewPlayers);
        _ -> loop(Players)
    end.

那里;看起来好多了。

在不同的终端窗口上运行Erlang程序时的异常

2 个答案: