以下代码适用于gen_tcp:connect()
函数调用中的{packet,0}
选项,但不适用于1,2和4(虽然我仅测试它为4,我假设1和2也不起作用)。我拥有的问题是为什么不这样做,重要的是使用一个在另一个之上?基本上Erlang文档没有提供关于数据包选项的详细说明,而Joe Armstrong编程Erlang也没有给出任何细节;他只是解释说数据包不是按顺序重组的,尽管我一直认为tcp数据包是在发送时收到的,与UDP不同。我有一个有趣的笔记是,this page上的客户端服务器有{packet,4}
作为选项,它工作正常,它与下面的代码非常相似。下面的代码使用{packet,4}
选项的服务器shell输出。Erlang:{packet,N}选项适用于N = 0但不是1,2,4?
Erlang R16A (erts-5.10) [smp:8:8] [async-threads:10]
Eshell V5.10 (abort with ^G)
1> cd("c:/erlang").
c:/erlang
ok
2> c(cp3).
{ok,cp3}
3> cp3:server().
Started Server:
<0.41.0>
Accept Server:
Pid <0.43.0>
Connection accepted
Accept Server:
Loop Server:
Error on socket #Port<0.2256> reason: einval
这是客户端的shell输出。
Erlang R16A (erts-5.10) [smp:8:8] [async-threads:10]
Eshell V5.10 (abort with ^G)
1> cd("c:/erlang").
c:/erlang
ok
2> cp3:client().
exit
3>
,这是所使用的代码,
-module(cp3).
-export([client/0, server/0,start/0,accept/1,enter_loop/1,loop/1]).
client() ->
{ok, Socket} = gen_tcp:connect("localhost", 4001,[binary, {packet, 4}]),
ok = gen_tcp:send(Socket, "packet"),
receive
{tcp,Socket,String} ->
io:format("Client received = ~p~n",[String]),
io:format("Client result = ~p~n",[String]),
gen_tcp:close(Socket)
after 1000 ->
exit
end.
server() ->
Pid = spawn(fun()-> start() end),
Pid.
start() ->
io:format("Started Server:~n"),
{ok, Socket} = gen_tcp:listen(4001, [binary, {packet, 4},{reuseaddr, true},{active, false}]),
accept(Socket).
accept(ListenSocket) ->
io:format("Accept Server:~n"),
case gen_tcp:accept(ListenSocket) of
{ok, Socket} ->
Pid = spawn(fun() ->
io:format("Connection accepted ~n", []),
enter_loop(Socket)
end),
io:format("Pid ~p~n",[Pid]),
gen_tcp:controlling_process(Socket, Pid),
Pid ! ack,
accept(ListenSocket);
Error ->
exit(Error)
end.
enter_loop(Socket) ->
%% make sure to acknowledge owner rights transmission finished
receive ack -> ok end,
loop(Socket).
loop(Socket) ->
io:format("Loop Server:~n"),
case gen_tcp:recv(Socket, 6) of
{ok, Data} ->
case Data of
<<"packet">> ->
io:format("Server replying = ~p~n",[Data]),
gen_tcp:send(Socket, Data),
loop(Socket)
end;
{error, Reason} ->
io:format("Error on socket ~p reason: ~p~n", [Socket, Reason])
end.