socket_server.erl

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%%% @author Oscar Hellström <oscar@hellstrom.st>
-module(socket_server).

-export([open/0, connect/2, listen/0, accept/1]).
-export([do_accept/1]).

open() ->
    {LS, Port} = listen(),
    Pid = accept(LS),
    {ok, Port} = inet:port(LS),
    Pid ! {connecting, self()},
    {ok, Socket} = gen_tcp:connect({127,0,0,1}, Port, [{active, false}]),
    receive accepted -> ok end,
    {LS, Socket}.

connect(Pid, Port) ->
    Pid ! {connecting, self()},
    {ok, Socket} = gen_tcp:connect({127,0,0,1}, Port, [{active, false}]),
    receive accepted -> ok end,
    Socket.

listen() ->
    {ok, LS} = gen_tcp:listen(0, [{active, false}, {ip, {127,0,0,1}}]),
    {ok, Port} = inet:port(LS),
    {LS, Port}.

accept(LS) ->
    spawn_link(?MODULE, do_accept, [LS]).

do_accept(LS) ->
    {ok, S} = gen_tcp:accept(LS),
    receive {connecting, Pid} ->  Pid ! accepted end,
    {error, closed} = gen_tcp:recv(S, 0).