修正Socket Base Distribution一节实例代码的Bug

拿到了Programming Erlang的电子书，研究一下Potian先前跟俺说的“Socket Base Distribution”部分代码，结果发现chat_client.erl（对应书上的Chapter 11 IRC Lite），运行出错，提示

引用

lib_chan_mm: protocol error:{login,"general","joe"}

查看lib_chan_mm.erl，可见如下代码：

loop1(Socket, Pid, Trace) ->
    receive
	{tcp, Socket, Bin} ->
	    Term = binary_to_term(Bin),
	    trace_it(Trace,{socketReceived, Term}),
	    Pid ! {chan, self(), Term},
	    loop1(Socket, Pid, Trace);
	{tcp_closed, Socket} ->  
	    trace_it(Trace, socketClosed),
	    Pid ! {chan_closed, self()};
	{'EXIT', Pid, Why} ->
	    trace_it(Trace,{controllingProcessExit, Why}),
	    gen_tcp:close(Socket);
	{setController, Pid1} ->
	    trace_it(Trace, {changedController, Pid}),
	    loop1(Socket, Pid1, Trace);
	{trace, Trace1} ->
	    trace_it(Trace, {setTrace, Trace1}),
	    loop1(Socket, Pid, Trace1);
	close ->
	    trace_it(Trace, closedByClient),
	    gen_tcp:close(Socket);
	{send, Term}  ->
	    trace_it(Trace, {sendingMessage, Term}),
	    gen_tcp:send(Socket, term_to_binary(Term)),
	    loop1(Socket, Pid, Trace);
	UUg ->
	    io:format("lib_chan_mm: protocol error:~p~n",[UUg]),
	    loop1(Socket, Pid, Trace)
    end.

可见此Middle Man进程接收到“{login,"general","joe"}”这样的原始数据了，估计是客户端代码直接发过去的，果然如此：

MM ! {login, Group, Nick},

MM ! {relay, Nick, Str},

居然有这样的代码在客户端。修正bug很简单，在 lib_chan_mm.erl 有这个函数：

send(Pid, Term)       -> Pid ! {send, Term}.

替换一下，将

MM ! {login, Group, Nick},

这类，换成

lib_chan_mm:send(MM, {login, Group, Nick}),

客户端可以了，但接着发现，服务器端出问题了

引用

2> lib_chan_mm: protocol error:ack
2> lib_chan_mm: protocol error:{msg,"joe",<0.35.0>,"I'm starting the group"}

检查chat_server.erl，最后将问题定位在chat_group.erl，修改

C ! ack,

foreach(fun({Pid,_}) -> Pid ! {msg, Nick, C, Str} end, L),

为

lib_chan_mm:send(C, ack),

foreach(fun({Pid,_}) -> lib_chan_mm:send(Pid, {msg, Nick, C, Str}) end, L),

再试，sigh，客户端又出问题

2> chat_client login unexpected:{chan,
                                 <0.40.0>,
                                 {msg,
                                     "joe",
                                     <0.45.0>,
                                     "I'm starting the group"}}

晕了，再次将

{MM, ack} ->

{MM,{msg,From,Pid,Str}} ->

改为

{chan, MM, ack} ->

{chan, MM,{msg,From,Pid,Str}} ->

重新编译和启动服务器和客户端，终于可以了

引用

3> chat_server:start().
lib_chan starting:"chat.conf"
ConfigData=[{port,2223},
            {service,chat,
                     password,
                     "AsDT67aQ",
                     mfa,
                     mod_chat_controller,
                     start,
                     []}]
true
4> mod_chat_controller off we go ...<0.45.0>
4> group controller received Msg={chan_closed,<0.45.0>}
4> server error should die with exit(normal) was:{mm_closed,<0.45.0>}
4> mod_chat_controller off we go ...<0.48.0>
4> group controller received Msg={chan,<0.48.0>,{relay,"joe"," haha"}}
4> group controller received Msg={chan,<0.48.0>,close}
4> mod_chat_controller off we go ...<0.51.0>
4> mod_chat_controller off we go ...<0.55.0>
4> mod_chat_controller off we go ...<0.53.0>
4> mod_chat_controller off we go ...<0.57.0>
4> group controller received Msg={chan,<0.51.0>,{relay,"joe"," welcome all"}}

引用

2> chat_client:test().
<0.39.0>
3> chat_client login unexpected:{'EXIT',<0.52.0>,connectorFinished}
3> chat_client login unexpected:{'EXIT',<0.48.0>,connectorFinished}
3> chat_client login unexpected:{'EXIT',<0.50.0>,connectorFinished}
3> chat_client login unexpected:{'EXIT',<0.46.0>,connectorFinished}

在弹出的窗口里面自由聊天吧。至于为什么客户端会输出“chat_client login unexpected:{'EXIT',<0.46.0>,connectorFinished}”这样的信息，是因为try_to_connect函数里面，exit(connectorFinished)执行后会发送一个'EXIT'事件给client进程。


顺便附上修改过后的代码吧，等此书正式release了，估计代码也改过来了吧。