[erlang-questions] Why this code not being infinite recursive?

[I Gusti Ngurah Oka Prinarjaya]

Hi,

OMG. Finally..... I know and understand how this code flowing. It takes
days for me to understand.
It turns out this code below:

{ok, AcceptorSocket} = gen_tcp:accept(ListenSocket),

is locking / blocking the execution of these lines:

1. spawn(fun() -> acceptor(ListenSocket) end),
2. handle(AcceptorSocket).

Then, after we doing a connection to the port via telnet, the locking /
blocking become released / unlocked / unblocked, then executing lines: 1
and  create new process,
lines: 2 listen / waiting the incoming message. Then make a new locking at
the new created process for the next telnet connection. Yes this is an
infinity recursive.
The base case is killing main process that started from start_server/1
. exit(Pid,
killed)

Thank you :)




Pada tanggal Jum, 14 Jun 2019 pukul 11.45 I Gusti Ngurah Oka Prinarjaya <
okaprinarjaya@REDACTED> menulis:

> Hi,
>
> I learn gen_tcp from learnyousomeerlangg book. I try to understand flow of
> code below.
> And i got confused with acceptor/1 . Because acceptor/1 call itself but
> have no base case and just execute once. It's not usual. Why?
> From my understanding it should be an infinity recursive.
>
> -module(naive_tcp).
> -compile(export_all).
>
> start_server(Port) ->
>   Pid = spawn_link(
>     fun() ->
>       io:format("Spawned at start_server()~n"),
>       {ok, ListenSocket} = gen_tcp:listen(Port, [binary, {active, false}]),
>       spawn(fun() -> acceptor(ListenSocket) end),
>       timer:sleep(infinity)
>     end
>   ),
>   {ok, Pid}.
>
> acceptor(ListenSocket) ->
>   io:format("I am acceptor~n"),
>   {ok, AcceptorSocket} = gen_tcp:accept(ListenSocket),
>   spawn(fun() -> acceptor(ListenSocket) end),
>   handle(AcceptorSocket).
>
> handle(AcceptorSocket) ->
>   inet:setopts(AcceptorSocket, [{active, once}]),
>   receive
>     {tcp, AcceptorSocket, <<"quit", _/binary>>} ->
>       gen_tcp:close(AcceptorSocket);
>     {tcp, AcceptorSocket, Message} ->
>       gen_tcp:send(AcceptorSocket, Message),
>       handle(AcceptorSocket)
>   end.
>
> Please enlightenment
>
> Thank you
>
>
>
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