[erlang-questions] What kind of objects can be a message type?

Lhfcws GMail <>
Fri Nov 21 13:05:47 CET 2014


Thanks a lot!  gen_tcp:controlling_process is indeed what I want.
And let me confirm your answer:
1.  Objects like socket and file handler can be pass in spawn arguments.
2.  But they can not be passed by ! message passing.

Am I right?
--------------

在 2014年11月21日,19:50,Niclas Eklund <> 写道:

> Hello again!
> 
> Forgot to answer your second question. Yes, you can spawn a new process that will "own" the connection, but then you need to use this function - http://www.erlang.org/doc/man/gen_tcp.html#controlling_process-2 You typically want  to keep the listen process rather lightweight (do very little) since using blocking accept is common and then the listen process needs to be restarted when doing a live code upgrade. See for example this code - https://github.com/erlang/otp/blob/maint/lib/orber/src/orber_iiop_net_accept.erl It's doing a bit more, i.e. only allows a certain number of concurrent incoming requests, but as you can see it's minimal.
> 
> /Nick
> 
> On 11/21/2014 12:43 PM, Niclas Eklund wrote:
>> Hi!
>> 
>> I'm afraid that you don't handle the returned values correctly. See this page - http://www.erlang.org/doc/man/gen_tcp.html - for more info. Should be:
>> 
>> server() ->
>>    {ok, LSock} = gen_tcp:listen(5678, [binary, {packet, 0},
>>                                        {active, false}]),
>>    {ok, Sock} = gen_tcp:accept(LSock),
>>    {ok, Bin} = do_recv(Sock, []),
>>    ok = gen_tcp:close(Sock),
>>    Bin.
>> 
>> do_recv(Sock, Bs) ->
>>    case gen_tcp:recv(Sock, 0) of
>>        {ok, B} ->
>>            do_recv(Sock, [Bs, B]);
>>        {error, closed} ->
>>            {ok, list_to_binary(Bs)}
>>    end.
>> 
>> /Nick
>> 
>> 
>> 
>> On 11/21/2014 08:44 AM, Lhfcws GMail wrote:
>>> Hi, I’m new to Erlang.
>>> I have a question about the message passed among the Erlang processes.
>>> 1. I create a Socket or FileHandler, can I use ! to send it to another process and still works well?
>>> 
>>> demo code:
>>> 
>>>    ListenSocket = gen_tcp:listen(1055, [{active, true}]),
>>>    Socket = gen_tcp:accept(ListenSocket),
>>>    From ! {new_socket, Socket}.
>>> 
>>> 
>>> 2. What if I invoking ’spawn’ to pass the Socket to the new process ?
>>> 
>>> demo code:
>>> 
>>>    NewProcess = fun(Socket) -> … end.
>>> 
>>>    ListenSocket = gen_tcp:listen(1055, [{active, true}]),
>>>    Socket = gen_tcp:accept(ListenSocket),
>>>    spawn(NewProcess, Socket).
>>> 
>>> =======
>>> 
>>> I know that the message in the receiver is a copy of the one in the sender, but I’m a little confused about the questions above. Could someone just explain this?
>>> Thank you.
>>> _______________________________________________
>>> erlang-questions mailing list
>>> 
>>> http://erlang.org/mailman/listinfo/erlang-questions
>> 
> 



More information about the erlang-questions mailing list