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I finished the first version of my OSCDispatch server in erlang.

The program defines a generic server and uses a callback function for the dispaching rules.

the oscdispatch.erl looks like this and uses a parameter in the module definition

-module(oscdispatch, [Dispatch]).
-export([start_server/0]).
-include("server_config.hrl").

start_server() ->
    spawn( fun() -> server(?server_port) end ).

server(Port) ->
    {ok, Socket} = gen_udp:open( Port, [binary] ),
    io:format( "socked opened ~p~n ", [Socket]),
    loop(Socket).

loop(Socket) ->
    receive
        {udp, Socket, Host, Port, Bin} ->
            Adr = binary_to_list(util:getadr(Bin)),
            io:format( "got: ~p~n", [{Host, Port, Adr}]),
            Dispatch:dispatch( Adr, Bin ),
            loop(Socket)
    end.

to use the server a module has to define the dispatch/2 function and create an instance of the oscdispatch module.

-module(demo).
-export([start/0, dispatch/2]).

start() ->
    S = oscdispatch:new(demo), %%% <- create an instance of the 
                               %%%    oscdispacht module using a parameter
    S:start_server().

%% define where to send the messages
dispatch( "/color" ++ _, Bin ) ->
    util:send( "localhost", 1234, Bin),
    util:send( "localhost", 1235, Bin);

dispatch( "/osc/midi" ++ _, Bin ) ->
    util:send( "localhost", 4002, Bin);

dispatch( _, _ ) ->
    io:format( "UNKNOWN ~n" ).

in util erl some utility functions for splitting strings and sending udp messages are defined

-module(util).
-export([send/3, getadr/1]).

%% send message to host/port
send( Host, Port, Bin) ->
    {ok, Socket} = gen_udp:open( 0, [binary] ),
    ok = gen_udp:send( Socket, Host, Port, Bin ),
    gen_udp:close( Socket ).

%% extract osc event address
getadr( Bin ) ->
    Len = msglen( Bin, 0 ),
    {Msg, _} = split_binary(Bin, Len),
    Msg.

%% Get Length of the first \0 based string
msglen(<<0, _/binary>>, Len) -> Len;

msglen(Bin, Len) ->
    { _, Next} = split_binary( Bin, 1 ),
    msglen( Next, Len + 1).

server_config.hrl is used to defined the listening port of the server app

-define(server_port, 4000).