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Added Erlang version
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‎README.md

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## Running
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### Erlang
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cd erlang
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./compile
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./start
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1> application:start(smtpd).
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### Go
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cd go

‎erlang/compile

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#!/bin/sh
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erlc -o ebin src/*.erl
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‎erlang/ebin/smtpd.app

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{application, smtpd,
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[{description, "A simple SMTP server"},
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{vsn, "0.1.0"},
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{modules, [smtpd_app,
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smtpd_sup,
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smtp_server, smtp_session]},
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{registered, [smtpd_sup]},
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{applications, [kernel, stdlib]},
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{mod, {smtpd_app, []}}
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]}.

‎erlang/src/smtp_server.erl

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%%%
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%%% Simple SMTP server in Erlang
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%%%
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%%% Author: Maarten Oelering
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%%%
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-module(smtp_server).
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-behaviour(gen_server).
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%% API
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-export([start_link/1]).
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%% callbacks
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-export([init/1, handle_call/3, handle_cast/2, handle_info/2,
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terminate/2, code_change/3]).
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-record(state, {lsock, hostname, session}).
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%%%===================================================================
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%%% API
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%%%===================================================================
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start_link({LSock, Hostname}) ->
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gen_server:start_link(?MODULE, [{LSock, Hostname}], []).
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%%%===================================================================
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%%% callbacks
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%%%===================================================================
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init([{LSock, Hostname}]) ->
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% force timeout and wait for connect in handle_info/2
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{ok, #state{lsock = LSock, hostname = Hostname}, 0}.
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handle_call(Request, _From, State) ->
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Reply = {ok, Request},
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{reply, Reply, State}.
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handle_cast(stop, State) ->
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{stop, normal, State}.
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%% data received on socket
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handle_info({tcp, _Socket, Data}, #state{session = Session} = State) ->
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case smtp_session:data_line(Session, Data) of
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{ok, NewSession} ->
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{noreply, State#state{session = NewSession}};
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{stop, NewSession} ->
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{stop, normal, State#state{session = NewSession}}
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end;
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%% socket closed by peer
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handle_info({tcp_closed, _Socket}, State) ->
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{stop, normal, State};
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handle_info(timeout, #state{lsock = LSock, hostname = Hostname} = State) ->
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% wait for connection
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{ok, Socket} = gen_tcp:accept(LSock),
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{ok, Session} = smtp_session:connect(Socket, Hostname),
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% start new acceptor process
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smtpd_sup:start_child(),
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{noreply, State#state{session = Session}};
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handle_info(_Info, State) ->
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{noreply, State}.
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terminate(_Reason, #state{session = Session} = _State) ->
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smtp_session:disconnect(Session),
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% ?? gen_tcp:close(Socket),
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ok.
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code_change(_OldVsn, State, _Extra) ->
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{ok, State}.
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%%%===================================================================
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%%% helpers
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%%%===================================================================
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‎erlang/src/smtp_session.erl

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%%%
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%%% Simple SMTP server in Erlang
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%%%
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%%% Author: Maarten Oelering
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%%%
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-module(smtp_session).
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%% API
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-export([connect/2, disconnect/1, data_line/2]).
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-record(session, {socket, mode, hostname}).
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%%%===================================================================
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%%% API
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%%%===================================================================
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connect(Socket, Hostname) ->
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gen_tcp:send(Socket, reply(220, lists:concat([Hostname, " ESMTP"]))),
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{ok, #session{socket = Socket, mode = command, hostname = Hostname}}.
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disconnect(_Session) ->
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{ok}.
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data_line(#session{mode = command} = Session, Data) ->
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Command = string:to_upper(string:substr(Data, 1, 4)),
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case Command of
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"HELO" ->
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send(Session, reply(250, Session#session.hostname)),
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{ok, Session};
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"EHLO" ->
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send(Session, reply(250, Session#session.hostname)),
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{ok, Session};
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"MAIL" ->
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send(Session, reply(250, "OK")),
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{ok, Session};
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"RCPT" ->
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send(Session, reply(250, "OK")),
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{ok, Session};
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"DATA" ->
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send(Session, reply(354, "End data with <CR><LF>.<CR><LF>")),
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{ok, Session#session{mode = data}};
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"QUIT" ->
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send(Session, reply(221, lists:concat([Session#session.hostname, " closing connection"]))),
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{stop, Session};
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_ ->
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send(Session, reply(500, "unrecognized command")),
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{ok, Session}
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end;
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data_line(#session{mode = data} = Session, Data) ->
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case Data of
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".\r\n" ->
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send(Session, reply(250, "OK")),
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{ok, Session#session{mode = command}};
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_ ->
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{ok, Session}
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end.
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%%%===================================================================
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%%% Implementation
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%%%===================================================================
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send(#session{socket = Socket}, Reply) ->
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gen_tcp:send(Socket, Reply).
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%% construct multi or singleline reply
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reply(_, []) -> [];
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reply(Code, [Tail]) when is_list(Tail) ->
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reply(Code, Tail);
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reply(Code, [Head | Tail]) when is_list(Head) ->
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[lists:concat([Code, "-", Head, "\r\n"]) | reply(Code, Tail)];
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reply(Code, Text) ->
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[lists:concat([Code, " ", Text, "\r\n"])].
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‎erlang/src/smtpd_app.erl

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%%%
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%%% Simple SMTP server in Erlang
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%%%
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%%% Author: Maarten Oelering
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%%%
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-module(smtpd_app).
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-behaviour(application).
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-export([start/2, stop/1]).
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-define(DEFAULT_PORT, 2525).
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start(_Type, _StartArgs) ->
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% open listen socket here, avoiding adding code to supervisors
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Port = case application:get_env(tcp_interface, port) of
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{ok, P} -> P;
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undefined -> ?DEFAULT_PORT
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end,
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% TODO: binary, {reuseaddr, true}, {keepalive, true}, {backlog, 30}
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{ok, LSock} = gen_tcp:listen(Port, [{active, true}, {packet, line}, {reuseaddr, true}]),
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% TODO: check for {error, Reason} return
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{ok, Hostname} = inet:gethostname(),
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% start supervisor
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case smtpd_sup:start_link({LSock, Hostname}) of
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{ok, Pid} ->
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io:format("server started~n"),
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% start first accept server
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smtpd_sup:start_child(),
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{ok, Pid};
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Other ->
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{error, Other}
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end.
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stop(_State) ->
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ok.
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‎erlang/src/smtpd_sup.erl

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%%%
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%%% Simple SMTP server in Erlang
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%%%
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%%% Author: Maarten Oelering
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%%%
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-module(smtpd_sup).
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-behaviour(supervisor).
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%% API
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-export([start_link/1, start_child/0]).
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%% callbacks
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-export([init/1]).
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%%%===================================================================
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%%% API
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%%%===================================================================
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start_link({LSock, Hostname}) ->
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supervisor:start_link({local, ?MODULE}, ?MODULE, [{LSock, Hostname}]).
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start_child() ->
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supervisor:start_child(?MODULE, []).
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%%%===================================================================
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%%% callbacks
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%%%===================================================================
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init([{LSock, Hostname}]) ->
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SupervisorSpec = {simple_one_for_one, 0, 1},
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ChildSpec = {smtp_server, {smtp_server, start_link, [{LSock, Hostname}]},
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temporary, brutal_kill, worker, [smtp_server]},
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{ok, {SupervisorSpec, [ChildSpec]}}.
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‎erlang/start

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#!/bin/sh
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echo ""
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echo "At the prompt, to start enter:"
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echo "1> application:start(smtpd)."
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echo "and to stop:"
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echo "2> q()."
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echo ""
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erl -pa ebin
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‎results.md

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### Erlang
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$ time smtp-source -c -d -l 32000 -m 10000 -N -s 30 127.0.0.1:2525
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10000
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real 0m2.693s
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user 0m0.291s
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sys 0m1.239s
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### Go
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$ time smtp-source -c -d -l 32000 -m 10000 -N -s 30 127.0.0.1:2525

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