Simple publish-subscribe service (for erlangdc)

pubsub.erl

-module(pubsub).

-export([handle/0, server/0]).

server() ->
    register(ps, handle()).

%% handle/0
handle() ->
    spawn(fun () -> handle([]) end).

%% handle/1
handle(Subscribers) ->
    receive
        {subscribe, Pid} ->
            io:format("Pid=~p subcribed!~n", [Pid]),
            handle([Pid|Subscribers]);
        {unsubscribe, Pid} ->
            io:format("Pid=~p unsubcribed!~n", [Pid]),
            handle(lists:delete(Pid, Subscribers));
        {message, Message} ->
            sendMessage(Message, Subscribers),
            handle(Subscribers);
        Unknown ->
            io:format("Unknown message: ~p~n", [Unknown]),
            handle(Subscribers)
    end.

sendMessage(_Message, []) -> ok;
sendMessage(Message, [First|Rest]) ->
    First ! Message,
    sendMessage(Message, Rest).

Start it up in one Erlang VM, named 'foo'. It registers the service as 'ps':

colin@Anna:~/Development/pubsub$ erl -sname foo
Erlang R14B03 (erts-5.8.4) [source] [smp:2:2] [rq:2] [async-threads:0] [kernel-poll:false]

Eshell V5.8.4  (abort with ^G)
(foo@Anna)1> pubsub:server().
true
(foo@Anna)2> ps ! {subscribe, self()}.
Pid=<0.38.0> subcribed!
{subscribe,<0.38.0>}

Start up another VM ('bar') and connect it to 'foo':

colin@Anna:~/Development/pubsub$ erl -sname bar
Erlang R14B03 (erts-5.8.4) [source] [smp:2:2] [rq:2] [async-threads:0] [kernel-poll:false]

Eshell V5.8.4  (abort with ^G)
(bar@Anna)1> node().
bar@Anna
(bar@Anna)2> nodes().
[]
(bar@Anna)3> net_adm:ping(foo@Anna).
pong
(bar@Anna)4> nodes().               
[foo@Anna]

Then send a message from 'bar':

(bar@Anna)5> Ps = {ps, foo@Anna}.
{ps,foo@Anna}
(bar@Anna)6> Ps ! {message, "test remote"}.
{message,"test remote"}

And receive it at 'foo':

(foo@Anna)3> flush().
Shell got "test remote"
ok