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Merge pull request atomvm#1419 from pguyot/w52/add-erl_epmd
Add `erl_epmd` These changes are made under both the "Apache 2.0" and the "GNU Lesser General Public License 2.1 or later" license terms (dual license). SPDX-License-Identifier: Apache-2.0 OR LGPL-2.1-or-later
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‎CHANGELOG.md‎

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@@ -23,6 +23,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
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- Added `supervisor:terminate_child/2`, `supervisor:restart_child/2` and `supervisor:delete_child/2`
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- Added `atomvm:subprocess/4` to perform pipe/fork/execve on POSIX platforms
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- Added `externalterm_to_term_with_roots` to efficiently preserve roots when allocating memory for external terms.
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- Added `erl_epmd` client implementation to epmd using `socket` module
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### Changed
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‎libs/estdlib/src/CMakeLists.txt‎

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@@ -28,6 +28,7 @@ set(ERLANG_MODULES
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calendar
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code
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crypto
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erl_epmd
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erts_debug
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ets
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gen_event

‎libs/estdlib/src/erl_epmd.erl‎

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%
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% This file is part of AtomVM.
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%
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% Copyright 2024 Paul Guyot <pguyot@kallisys.net>
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%
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% Licensed under the Apache License, Version 2.0 (the "License");
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% you may not use this file except in compliance with the License.
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% You may obtain a copy of the License at
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%
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% http://www.apache.org/licenses/LICENSE-2.0
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%
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% Unless required by applicable law or agreed to in writing, software
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% distributed under the License is distributed on an "AS IS" BASIS,
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% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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% See the License for the specific language governing permissions and
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% limitations under the License.
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%
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% SPDX-License-Identifier: Apache-2.0 OR LGPL-2.1-or-later
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%
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%%-----------------------------------------------------------------------------
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%% @doc An implementation of the Erlang/OTP erl_epmd interface.
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%%
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%% This module implements a strict subset of the Erlang/OTP erl_epmd
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%% interface.
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%% @end
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%%-----------------------------------------------------------------------------
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-module(erl_epmd).
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% API
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-export([
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start_link/0,
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stop/0,
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port_please/2,
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register_node/2,
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names/1
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]).
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% gen_server
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-behaviour(gen_server).
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-export([
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init/1,
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handle_call/3,
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handle_cast/2,
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handle_info/2,
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terminate/2,
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code_change/3
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]).
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-record(state, {socket = undefined}).
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-define(EPMD_PORT, 4369).
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-define(TIMEOUT, 5000).
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-define(NAMES_REQ, 110).
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-define(ALIVE2_X_RESP, 118).
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-define(PORT2_RESP, 119).
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-define(ALIVE2_REQ, 120).
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-define(ALIVE2_RESP, 121).
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-define(PORT_PLEASE2_REQ, 122).
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-define(TCP_INET4_PROTOCOL, 0).
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-define(ERLANG_NODE_TYPE, 77).
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-define(VERSION, 6).
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-record(receive_port2_resp, {
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port_no :: non_neg_integer(),
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highest_version :: non_neg_integer(),
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lowest_version :: non_neg_integer()
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}).
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-record(alive2_resp, {
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creation :: non_neg_integer()
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}).
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%% @doc Start EPMD client
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-spec start_link() -> {ok, pid()}.
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start_link() ->
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gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).
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%% @doc Stop EPMD client-
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-spec stop() -> ok.
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stop() ->
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gen_server:call(?MODULE, stop, infinity).
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%% @param Name name of the node to get the port of
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%% @param Host host of the node to get the port of
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%% @doc Get the port and version of a node on a given host.
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%% This function will connect to epmd on the host.
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-spec port_please(Name :: iodata(), Host :: inet:hostname() | inet:ip_address()) ->
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{port, inet:port_number(), non_neg_integer()} | noport.
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port_please(Name, Host) ->
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case inet:getaddr(Host, inet) of
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{ok, IP} ->
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{ok, Socket} = socket:open(inet, stream, tcp),
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case socket:connect(Socket, #{addr => IP, port => ?EPMD_PORT, family => inet}) of
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ok ->
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NameBin = iolist_to_binary(Name),
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Result =
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case send_request(Socket, <<?PORT_PLEASE2_REQ, NameBin/binary>>) of
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{ok, #receive_port2_resp{
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port_no = PortNo,
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highest_version = HighVersion,
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lowest_version = LowVersion
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}} when HighVersion >= ?VERSION andalso LowVersion =< ?VERSION ->
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{port, PortNo, ?VERSION};
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{ok, #receive_port2_resp{port_no = PortNo}} ->
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{port, PortNo, 0};
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{ok, _Unexpected} ->
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noport;
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{error, _} ->
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noport
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end,
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ok = socket:close(Socket),
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Result;
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{error, _} ->
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noport
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end;
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{error, _} ->
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noport
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end.
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%% @param Host the host to connect to
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%% @return a list of names and ports of registered nodes
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%% @doc Get the names and ports of all registered nodes
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%% This function will connect to epmd on localhost.
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-spec names(Host :: inet:hostname() | inet:ip_address()) ->
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{ok, [{string(), inet:port_number()}]} | {error, any()}.
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names(Host) ->
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case inet:getaddr(Host, inet) of
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{ok, IP} ->
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{ok, Socket} = socket:open(inet, stream, tcp),
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case socket:connect(Socket, #{addr => IP, port => ?EPMD_PORT, family => inet}) of
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ok ->
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Result =
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case socket:send(Socket, <<1:16, ?NAMES_REQ>>) of
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ok ->
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case socket:recv(Socket, 4, ?TIMEOUT) of
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{ok, <<?EPMD_PORT:32>>} ->
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receive_names_loop(Socket, <<>>, []);
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{ok, Unexpected} ->
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{error, {unexpected, Unexpected}};
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{error, _} = ErrRecv ->
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ErrRecv
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end;
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{error, _} = ErrSend ->
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ErrSend
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end,
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ok = socket:close(Socket),
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Result;
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{error, _} = ErrConnect ->
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ErrConnect
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end;
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{error, _} = ErrGetAddr ->
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ErrGetAddr
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end.
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receive_names_loop(Socket, AccBuffer, AccL) ->
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case binary:split(AccBuffer, <<"\n">>) of
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[AccBuffer] ->
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case socket:recv(Socket, 0, ?TIMEOUT) of
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{error, closed} when AccBuffer =:= <<>> -> {ok, lists:reverse(AccL)};
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{error, _} = ErrT -> ErrT;
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{ok, Data} -> receive_names_loop(Socket, <<Data/binary, AccBuffer/binary>>, AccL)
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end;
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[<<"name ", RestLine/binary>>, RestBuffer] ->
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case binary:split(RestLine, <<" at port ">>) of
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[NameBin, PortBin] ->
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try binary_to_integer(PortBin) of
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Port ->
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receive_names_loop(Socket, RestBuffer, [
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{binary_to_list(NameBin), Port} | AccL
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])
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catch
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error:badarg ->
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{error, {unexpected, <<"name ", RestLine/binary>>}}
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end;
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[_] ->
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{error, {unexpected, <<"name ", RestLine/binary>>}}
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end;
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[UnexpectedLine, _RestBuffer] ->
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{error, {unexpected, UnexpectedLine}}
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end.
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%% @param Name name to register
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%% @param Port port to register
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%% @doc Register to local epmd and get a creation number
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-spec register_node(Name :: iodata(), Port :: inet:port_number()) ->
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{ok, non_neg_integer()} | {error, any()}.
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register_node(Name, Port) ->
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gen_server:call(?MODULE, {register_node, Name, Port}, infinity).
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%% @hidden
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init([]) ->
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State = #state{},
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{ok, State}.
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%% @hidden
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handle_call({register_node, _Name, _Port}, _From, #state{socket = Socket} = State) when
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Socket =/= undefined
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->
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{reply, {error, already_registered}, State};
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handle_call({register_node, Name, Port}, _From, #state{} = State) ->
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{ok, Socket} = socket:open(inet, stream, tcp),
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case socket:connect(Socket, #{addr => {127, 0, 0, 1}, port => ?EPMD_PORT, family => inet}) of
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ok ->
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NameBin = iolist_to_binary(Name),
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NameLen = byte_size(NameBin),
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Packet =
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<<?ALIVE2_REQ, Port:16, ?ERLANG_NODE_TYPE, ?TCP_INET4_PROTOCOL, ?VERSION:16,
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?VERSION:16, NameLen:16, NameBin/binary, 0:16>>,
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case send_request(Socket, Packet) of
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{ok, #alive2_resp{creation = Creation}} ->
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{reply, {ok, Creation}, State#state{socket = Socket}};
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{error, _} = RequestErr ->
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socket:close(Socket),
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{reply, RequestErr, State}
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end;
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{error, _} = ConnectErr ->
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socket:close(Socket),
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{reply, ConnectErr, State}
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end;
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handle_call(stop, _From, State) ->
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{stop, shutdown, ok, State}.
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%% @hidden
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handle_cast(_Message, State) ->
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{noreply, State}.
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%% @hidden
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handle_info(_Message, State) ->
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{noreply, State}.
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%% @hidden
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terminate(_Reason, #state{socket = Socket}) ->
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case Socket of
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undefined -> ok;
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_ -> socket:close(Socket)
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end,
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ok.
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%% @hidden
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code_change(_OldVsn, State, _Extra) ->
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{ok, State}.
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send_request(Socket, Request) ->
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RequestSize = byte_size(Request),
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case socket:send(Socket, <<(RequestSize):16, Request/binary>>) of
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ok ->
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case socket:recv(Socket, 1, ?TIMEOUT) of
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{ok, <<?PORT2_RESP>>} ->
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receive_port2_resp(Socket);
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{ok, <<?ALIVE2_X_RESP>>} ->
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receive_alive2_x_resp(Socket);
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{ok, <<?ALIVE2_RESP>>} ->
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receive_alive2_resp(Socket);
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{error, _} = ErrorRecv2 ->
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ErrorRecv2
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end;
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{error, _} = ErrorSend ->
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ErrorSend
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end.
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receive_port2_resp(Socket) ->
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case socket:recv(Socket, 1, ?TIMEOUT) of
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{ok, <<0>>} ->
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case socket:recv(Socket, 10, ?TIMEOUT) of
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{ok,
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<<PortNo:16, _NodeType, _Protocol, HighestVersion:16, LowestVersion:16,
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NameLen:16>>} ->
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case socket:recv(Socket, NameLen + 2, ?TIMEOUT) of
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{ok, <<_Name:NameLen/binary, ExtraLen:16>>} ->
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case ExtraLen of
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0 ->
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{ok, #receive_port2_resp{
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port_no = PortNo,
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highest_version = HighestVersion,
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lowest_version = LowestVersion
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}};
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N ->
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case socket:recv(Socket, N, ?TIMEOUT) of
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{ok, _ExtraData} ->
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{ok, #receive_port2_resp{
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port_no = PortNo,
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highest_version = HighestVersion,
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lowest_version = LowestVersion
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}};
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{error, _} = ErrT1 ->
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ErrT1
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end
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end;
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{error, _} = ErrT2 ->
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ErrT2
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end;
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{error, _} = ErrT3 ->
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ErrT3
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end;
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{ok, <<N>>} ->
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{error, N};
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{error, _} = ErrT4 ->
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ErrT4
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end.
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receive_alive2_x_resp(Socket) ->
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case socket:recv(Socket, 5, ?TIMEOUT) of
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{ok, <<0, Creation:32>>} -> {ok, #alive2_resp{creation = Creation}};
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{ok, <<Err, _:32>>} -> {error, Err};
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{error, _} = ErrT -> ErrT
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end.
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receive_alive2_resp(Socket) ->
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case socket:recv(Socket, 3, ?TIMEOUT) of
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{ok, <<0, Creation:16>>} -> {ok, #alive2_resp{creation = Creation}};
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{ok, <<Err, _:16>>} -> {error, Err};
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{error, _} = ErrT -> ErrT
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end.

‎tests/libs/estdlib/CMakeLists.txt‎

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test_apply
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test_binary
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test_calendar
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test_epmd
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test_gen_event
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test_gen_server
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test_gen_statem

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