Erlang组播

Question

你如何在Erlang中使用gen_udp进行多播？我知道它在代码中,它背后没有文档.发送数据显而易见且简单.我想知道如何添加会员资格.不仅在启动时添加成员资格,而且在运行时添加成员资格也很有用.

Answer 1

以下是有关如何收听Bonjour/Zeroconf流量的示例代码.

-module(zcclient).

-export([open/2,start/0]).
-export([stop/1,receiver/0]).

open(Addr,Port) ->
   {ok,S} = gen_udp:open(Port,[{reuseaddr,true}, {ip,Addr}, {multicast_ttl,4}, {multicast_loop,false}, binary]),
   inet:setopts(S,[{add_membership,{Addr,{0,0,0,0}}}]),
   S.

close(S) -> gen_udp:close(S).

start() ->
   S=open({224,0,0,251},5353),
   Pid=spawn(?MODULE,receiver,[]),
   gen_udp:controlling_process(S,Pid),
   {S,Pid}.

stop({S,Pid}) ->
   close(S),
   Pid ! stop.

receiver() ->
   receive
       {udp, _Socket, IP, InPortNo, Packet} ->
           io:format("~n~nFrom: ~p~nPort: ~p~nData: ~p~n",[IP,InPortNo,inet_dns:decode(Packet)]),
           receiver();
       stop -> true;
       AnythingElse -> io:format("RECEIVED: ~p~n",[AnythingElse]),
           receiver()
   end. 

Answer 2

已回答多播发送,接收需要订阅多播组.

它(仍然)似乎没有记录,但之前已经在erlang-questions邮件列表中进行了介绍.http://www.erlang.org/pipermail/erlang-questions/2003-March/008071.html

    {ok, Socket} = gen_udp:open(Port, [binary, {active, false},
                                       {reuseaddr, true},{ip, Addr}, 
                                       {add_membership, {Addr, LAddr}}]).

其中Addr是组播组,LAddr是本地接口.(代码由mog提供)

可以传递上面使用的相同选项以inet:setopts包括{drop_membership, {Addr, LAddr}}停止收听该组.