我要做的是让gen_server进程接受一个新客户端并立即生成一个新子进程来处理下一个客户端。我看到的问题是，当套接字完成并因此终止时，它也会关闭监听套接字，我无法弄清楚为什么，即使它不再引用它。
知道我做错了吗？
gen_server：
-module(simple_tcp).
-behaviour(gen_server).
%% API
-export([start_link/1, stop/0, start/0, start/1]).
%% gen-server callbacks
-export([init/1, handle_call/3, handle_cast/2, handle_info/2, terminate/2, code_change/3]).
-define(SERVER, ?MODULE).
-define(DEFAULT_PORT, 1055).
-record(state, {port, lsock}).
start_link({port, Port}) ->
gen_server:start_link(?MODULE, [{port, Port}], []);
start_link({socket, Socket}) ->
gen_server:start_link(?MODULE, [{socket, Socket}], []).
start({port, Port}) ->
simple_tcp_sup:start_child({port, Port});
start({socket, Socket}) ->
simple_tcp_sup:start_child({socket, Socket}).
start() ->
start({port, ?DEFAULT_PORT}).
stop() ->
gen_server:cast(?SERVER, stop).
% Callback functions
init([{port, Port}]) ->
{ok, LSock} = gen_tcp:listen(Port, [{active, true},{reuseaddr, true}]),
init([{socket, LSock}]);
init([{socket, Socket}]) ->
io:fwrite("Starting server with socket: ~p~n", [self()]),
{ok, Port} = inet:port(Socket),
{ok, #state{port=Port, lsock=Socket}, 0}.
handle_call(_Msg, _From, State) ->
{noreply, State}.
handle_cast(stop, State) ->
{stop, ok, State}.
handle_info({tcp, Socket, RawData}, State) ->
gen_tcp:send(Socket, io_lib:fwrite("Received raw data: ~p~n", [RawData])),
{noreply, State};
handle_info({tcp_error, _Socket, Reason}, State) ->
io:fwrite("Error: ~p~n", [Reason]),
{stop, normal, State};
handle_info(timeout, #state{lsock = LSock} = State) ->
case gen_tcp:accept(LSock) of
{ok, Sock} ->
io:fwrite("Accepting connection...~p~n", [self()]),
start({socket, LSock}),
{noreply, #state{lsock=Sock}};
{error, Reason} ->
io:fwrite("Error: ~p, ~p~n", [Reason, self()]),
{stop, normal, State}
end;
handle_info({tcp_closed, _Port}, State) ->
io:fwrite("Socket closed: ~p~n", [self()]),
simple_tcp_sup:kill_child(self()),
{stop, normal, State}.
terminate(_Reason, _State) ->
io:fwrite("Shutting down server: ~p~n", [self()]),
ok.
code_change(_OldVsn, State, _Extra) ->
{ok, State}.
主管：
-module(simple_tcp_sup).
-behaviour(supervisor).
-export([start_link/0,
start_child/1
]).
-export([init/1]).
-define(SERVER, ?MODULE).
start_link() ->
supervisor:start_link({local, ?SERVER}, ?MODULE, []).
start_child({socket, Socket}) ->
io:fwrite("Spawning child with socket...~n"),
supervisor:start_child(?SERVER, [{socket, Socket}]);
start_child({port, Port}) ->
io:fwrite("Spawning child with port...~n"),
supervisor:start_child(?SERVER, [{port, Port}]).
init([]) ->
Element = {simple_tcp, {simple_tcp, start_link, []},
temporary, brutal_kill, worker, [simple_tcp]},
Children = [Element],
RestartStrategy = {simple_one_for_one, 0, 1},
{ok, {RestartStrategy, Children}}.
答案 0 :(得分：5)
您的第三个handle_info撤消了Sock和LSock的角色。它应该将Sock传递给子进程并保持其自己的状态不被修改。
State（#state{lsock=Sock}）是不好的业力，你应该总是从当前的State（State）派生新的State#state{lsock=Sock}，以防您以后添加更多状态变量。实际上，这有一个错误（虽然是一个良性的），因为你丢弃了端口号。
答案 1 :(得分：1)
好吧，我建议您让Socket的东西由与gen_server异步通信的单独进程处理，并且linked与它一起使用。我有一个示例代码段，可以向您展示如何完成此操作。 gen_server启动并生成TCP侦听器，该侦听器在成功获取侦听套接字后通知gen_server更改其内部状态。
我从上到下安排了代码。所有相关功能都已展示。
专注于套接字处理流程以及它们如何与gen_server进行交互
-define(PEER_CLIENT_TIMEOUT,timer:seconds(20)).
-define(PORT_RANGE,{10245,10265}).
-define(DEBUG(X,Y),error_logger:info_msg(X,Y)).
-define(ERROR(L),error_logger:error_report(L)).
-define(SOCKET_OPTS(IP),[inet,binary,{backlog,100},{packet,0},
{reuseaddr,true},{active,true},
{ip,IP}]).
%%----------------------------------------------------
%% gen_server starts here....
start(PeerName)->
gen_server:start_link({local,?MODULE},?MODULE,PeerName,[]).
%%%-------------------------------------------
%% Gen_server init/1 function
init(PeerName)->
process_flag(trap_exit,true),
%% starting the whole Socket chain below..
start_link_listener(),
%% Socket stuff started, gen_server can now wait for async
%% messages
{ok,[]}.
%%% ---- Socket handling functions ---------
%% Function: start_link_listener/0
%% Purpose: Starts the whole chain of listening
%% and waiting for connections. Executed
%% directly by the gen_server process, But
%% spawns a separate process to do the rest
start_link_listener()->
Ip_address = get_myaddr(),
spawn_link(fun() -> listener(?SOCKET_OPTS(Ip_address)) end).
%%%----------------------------------------------
%% Function: get_myaddr/0
%% Purpose: To pick the active IP address on my machine to
%% listen on
get_myaddr()->
?DEBUG("Server> Trying to extract My Local Ip Address....",[]),
{ok,Name} = inet:gethostname(),
{ok,IP} = inet:getaddr(Name,inet),
?DEBUG("Server> Found Alive Local IP address: ~p.....~n",[IP]),
IP.
%%%--------------------------------------------------
%% Function: listener/1, executed in a separate process
%% Purpose: Tries a given ?PORT_RANGE, with the given Socket Options
%% Once it acquires a ListenSocket, it will cast the gen_server!
listener(SocketOpts)->
process_flag(trap_exit,true),
Ports = lists:seq(element(1,?PORT_RANGE),element(2,?PORT_RANGE)),
case try_listening(SocketOpts,Ports) of
{ok,Port,LSocket}->
PP = proplists:get_value(ip,SocketOpts),
?MODULE:started_listener(Port,PP,LSocket),
accept_connection(LSocket);
{error,failed} -> {error,failed,SocketOpts}
end.
try_listening(_Opts,[])-> {error,failed};
try_listening(Opts,[Port|Rest])->
case gen_tcp:listen(Port,Opts) of
{ok,Listen_Socket} -> {ok,Port,Listen_Socket};
{error,_} -> try_listening(Opts,Rest)
end.
%%%---------------------------------------------------------
%% Helper Functions for Converting IP Address from tuple
%% to string and vice versa
str(X) when is_integer(X)-> integer_to_list(X).
formalise_ipaddress({A,B,C,D})->
str(A) ++ "." ++ str(B) ++ "." ++ str(C) ++ "." ++ str(D).
unformalise_address(String)->
[A,B,C,D] = string:tokens(String,"."),
{list_to_integer(A),list_to_integer(B),list_to_integer(C),list_to_integer(D)}.
%%%--------------------------------------------------
%% Function: get_source_connection/1
%% Purpose: Retrieving the IP and Port at the other
%% end of the connection
get_source_connection(Socket)->
try inet:peername(Socket) of
{ok,{IP_Address, Port}} ->
[{ipAddress,formalise_ipaddress(IP_Address)},{port,Port}];
_ -> failed_to_retrieve_address
catch
_:_ -> failed_to_retrieve_address
end.
%%%-----------------------------------------------------
%% Function: accept_connection/1
%% Purpose: waits for a connection and re-uses the
%% ListenSocket by spawning another thread
%% to take it and listen too. It casts the gen_server
%% at each connection and provides details about it.
accept_connection(ListenSocket)->
case gen_tcp:accept(ListenSocket,infinity) of
{ok, Socket}->
%% re-use the ListenSocket below.....
spawn_link(fun() -> accept_connection(ListenSocket) end),
OtherEnd = get_source_connection(Socket),
?MODULE:accepted_connection(OtherEnd),
loop(Socket,OtherEnd);
{error,_} = Reason ->
?ERROR(["Listener has failed to accept a connection",
{listener,self()},{reason,Reason}])
end.
%%%-------------------------------------------------------------------------
%% Function: loop/2
%% Purpose: TCP reception loop, it casts the gen_server
%% as soon as it receives something. gen_server
%% is responsible for generating reponse
%% OtherEnd ::= [{ipAddress,StringIPAddress},{Port,Port}] or 'failed_to_retrieve_address'
loop(Socket,OtherEnd)->
receive
{tcp, Socket, Data}->
?DEBUG("Acceptor: ~p has received a binary message from: ~p~n",[self(),OtherEnd]),
Reply = ?MODULE:incoming_binary_message(Data,OtherEnd),
gen_tcp:send(Socket,Reply),
gen_tcp:close(Socket),
exit(normal);
{tcp_closed, Socket} ->
?DEBUG("Acceptor: ~p. Socket closed by other end: ~p~n",[self(),OtherEnd]),
?MODULE:socket_closed(OtherEnd),
exit(normal);
Any -> ?DEBUG("Acceptor: ~p has received a message: ~p~n",[self(),Any])
end.
%%%----------------------------------------------
%% Gen_server Asynchronous APIs
accepted_connection(failed_to_retrieve_address)-> ok;
accepted_connection([{ipAddress,StringIPAddress},{Port,Port}])->
gen_server:cast(?MODULE,{connected,StringIPAddress,Port}).
socket_closed(failed_to_retrieve_address)-> ok;
socket_closed([{ipAddress,StringIPAddress},{Port,Port}])->
gen_server:cast(?MODULE,{socket_closed,StringIPAddress,Port}).
incoming_binary_message(Data,_OtherEnd)-> %% expecting a binary reply
case analyse_protocol(Data) of
wrong -> term_to_binary("protocol violation!");
Val -> gen_server:call(?MODULE,{request,Val},infinity)
end.
%%% -------------------- handle cast ------------------------------------------
handle_cast({listener_starts,_Port,_MyTupleIP,_LSocket} = Object,State)->
NewState = do_something_with_the_listen_report(Object),
{noreply,NewState};
handle_cast({connected,_StringIPAddress,_Port} = Object,State)->
NewState = do_something_with_the_connection_report(Object),
{noreply,NewState};
handle_cast({socket_closed,_StringIPAddress,_Port} = Object,State)->
NewState = do_something_with_the_closed_connection_report(Object),
{noreply,NewState};
handle_cast(Any,State)->
?DEBUG("Server> I have been casted some unknown message: ~p~n",[Any]),
{noreply,State}.
%%%% ---------------------- handle call --------------
handle_call({request,Val},_,State)->
{NewState,Reply} = req(Val,State),
{reply,Reply,NewState};
handle_call(_,_,State)-> {reply,[],State}.
req(Val,State)->
%% modify gen_server state and
%% build reply
{NewState,Reply} = modify_state_and_get_reply(State,Val),
{NewState,Reply}.
%%------------------- terminate/2 --------------------
terminate(_Reason,_State)-> ok.
%%----------------- code_change/3 ------------------
code_change(_,State,_)-> {ok,State}.
使用gen_server的异步功能，我们可以处理来自单独链接进程的套接字详细信息。然后，这些进程将通过cast与gen_server进行通信，而不会阻止gen_server的并发性。