Eine ernsthafte Lösung sollte die OTP-Verhaltensweisen (gen_server, supervisor ...) wie von Steve vorgeschlagen verwenden. Jedenfalls habe ich ein kleines Beispielmodul geschrieben, das sowohl einen Server als auch Clients implementiert und das auf einem Knoten beispielsweise mit dem Befehl erl -sname test gestartet werden kann (oder mehrere Knoten mit erl -sname node1, erl -sname node2 ...).
es enthält auch ein Beispiel für eine Shell-Sitzung, die die meisten Fälle veranschaulicht, ich hoffe, es kann Ihnen helfen, den Austausch zu verfolgen, synchron oder asynchron zwischen Prozessen.
HINWEIS:der Zugriff auf die Benutzerliste ist nicht gleichzeitig, es ist nicht möglich, wenn die Liste von einem Serverprozess gehört, wie es in diesem Beispiel ist. Aus diesem Grund schlägt Steve vor, eine ETS zu verwenden, um die Informationen zu speichern und echte gleichzeitige Zugriffe auszuführen. Ich habe versucht, das Beispiel mit Schnittstellen zu schreiben, die ein schnelles Refactoring mit ETS statt Tupel-Liste erlauben sollten.
-module(example).
-export([server/0,server_stop/1,server_register_name/2,server_get_address/2, server_quit/2, % server process and its interfaces
client/1,quit/1,register_name/2,get_address/2,send_message/3,print_messages/1, % client process and its interfaces
trace/0]). % to call the tracer for a nice message view
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Client interface
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
client(Node) ->
% connect the current node to the servernode given in parameter
% it will fail if the connection cannot be established
true = net_kernel:connect_node(Node),
% spawn a client process
spawn(fun() -> client([],unregistered,{server,Node}) end).
register_name(ClientPid,Name) ->
% use a helper to facilitate the trace of everything
send_trace(ClientPid,{register_name,self(),Name}),
% wait for an answer, it is then a synchronous call
receive
% no work needed, simply return any value
M -> M
after 1000 ->
% this introduce a timeout, if no answer is received after 1 second, consider it has failed
no_answer_from_client
end.
get_address(ClientPid,UserName) ->
send_trace(ClientPid,{get_address,self(),UserName}),
% wait for an answer, it is then a synchronous call
receive
% in this case, if the answer is tagged with ok, extract the Value (will be a Pid)
{ok,Value} -> Value;
M -> M
after 1000 ->
no_answer_from_client
end.
send_message(ClientPid,To,Message) ->
% simply send the message, it is asynchronous
send_trace(ClientPid,{send_message,To,Message}).
print_messages(ClientPid) ->
send_trace(ClientPid,print_messages).
quit(ClientPid) ->
send_trace(ClientPid,quit).
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% client local functions
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
client(Messages,Name,Server) ->
receive
{register_name,From,UserName} when Name == unregistered ->
% if not yet registered send the request to the server and
% backward the answer to the requester
Answer = server_register_name(Server,UserName),
send_trace(From,Answer),
NName = case Answer of
registered -> UserName;
_ -> Name
end,
client(Messages,NName,Server);
{register_name,From,_} ->
% if already registered reject the request
send_trace(From,{already_registered_as,Name}),
client(Messages,Name,Server);
{get_address,From,UserName} when Name =/= unregistered ->
Answer = server_get_address(Server,UserName),
send_trace(From,Answer),
client(Messages,Name,Server);
{send_message,To,Message} ->
% directly send the message to the user, the server is not concerned
send_trace(To,{new_message,{erlang:date(),erlang:time(),Name,Message}}),
client(Messages,Name,Server);
print_messages ->
% print all mesages and empty the queue
do_print_messages(Messages),
client([],Name,Server);
quit ->
server_quit(Server,Name);
{new_message,M} ->
% append the new message
client([M|Messages],Name,Server);
_ ->
client(Messages,Name,Server)
end.
do_print_messages(Messages) ->
lists:foreach(fun({D,T,W,M}) -> io:format("from ~p, at ~p on ~p, received ~p~n",[W,T,D,M]) end,Messages).
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Server interface
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
server() ->
true = register(server,spawn(fun() -> server([]) end)),
node().
server_stop(Server) ->
send_trace(Server,stop).
server_register_name(Server,User) ->
send_trace(Server,{register_name,self(),User}),
receive
M -> M
after 900 ->
no_answer_from_server
end.
server_get_address(Server,User) ->
send_trace(Server,{get_address,self(),User}),
receive
M -> M
after 900 ->
no_answer_from_server
end.
server_quit(Server,Name) ->
send_trace(Server,{quit,Name}).
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% server local functions
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
server(Users) ->
receive
stop ->
ok;
{register_name,From,User} ->
case lists:keyfind(User,1,Users) of
false ->
send_trace(From,registered),
server([{User,From}|Users]);
_ ->
send_trace(From,{already_exist,User}),
server(Users)
end;
{get_address,From,User} ->
case lists:keyfind(User,1,Users) of
false ->
send_trace(From,{does_not_exist,User}),
server(Users);
{User,Pid} ->
send_trace(From,{ok,Pid}),
server(Users)
end;
{quit,Name} ->
server(lists:keydelete(Name,1,Users))
end.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% global
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
trace() ->
% start a collector, a viewer and trace the "trace_me" ...
et_viewer:start([{trace_global, true}, {trace_pattern, {et,max}},{max_actors,20}]).
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% helpers
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
send_trace(To,Message) ->
% all messages will be traced by "et"
et:trace_me(50,self(),To,Message,[]),
To ! Message.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% shell commands
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% c(example).
% example:trace().
% N = node().
% C1 = example:client(N).
% example:register_name(pid(0,5555,0),"fails").
% example:register_name(C1,"fails_again").
% example:server().
% example:register_name(C1,"Joe").
% C2 = example:client(N).
% example:register_name(C2,"Bob").
% example:print_messages(C1).
% C2 = example:get_address(C1,"Bob").
% example:send_message(C1,C2,"Hi Bob!").
% example:send_message(C1,C2,"Hi Bob! are you there?").
% example:print_messages(C2).
% example:send_message(C2,C1,"Hi Joe! Got your message.").
% example:print_messages(C2).
% example:print_messages(C1).
% example:quit(C1).
% example:get_address(C2,"Joe").
% example:server_stop({server,N}).
% example:get_address(C2,"Joe").
% example:get_address(C1,"Bob").
hier ein Auszug aus der Ereignisanzeige:
neben Steve Antwort, ich bot ein „Spielzeug“ Modul zu zeigen, wie es funktioniert. – Pascal