diff --git a/src/sctp_handler.erl b/src/sctp_handler.erl
new file mode 100644
index 0000000..333d551
--- /dev/null
+++ b/src/sctp_handler.erl
@@ -0,0 +1,163 @@
+% SCTP Handler for gateway between MSC and STP, transparently
+% rewriting addresses on the fly
+
+% (C) 2011 by Harald Welte <laforge@gnumonks.org>
+% (C) 2011 OnWaves
+%
+% All Rights Reserved
+%
+% This program is free software; you can redistribute it and/or modify
+% it under the terms of the GNU Affero General Public License as
+% published by the Free Software Foundation; either version 3 of the
+% License, or (at your option) any later version.
+%
+% This program is distributed in the hope that it will be useful,
+% but WITHOUT ANY WARRANTY; without even the implied warranty of
+% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+% GNU General Public License for more details.
+%
+% You should have received a copy of the GNU Affero General Public License
+% along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+
+-module(sctp_handler).
+-author("Harald Welte <laforge@gnumonks.org>").
+-export([init/5, handle_sctp/2]).
+
+-include_lib("kernel/include/inet.hrl").
+-include_lib("kernel/include/inet_sctp.hrl").
+
+%-include("m2ua.hrl").
+%-include("mtp3.hrl").
+%-include("isup.hrl").
+%-include("sccp.hrl").
+
+-record(loop_data,
+	{msc_sock, msc_local_ip, msc_remote_ip, msc_remote_port,
+	 msc_local_port, msc_assoc_id, 
+	 stp_sock, stp_remote_ip, stp_remote_port, stp_assoc_id
+	}).
+
+-define(COMMON_SOCKOPTS, [{active, once}, {reuseaddr, true}]).
+
+% initialize the sockets towards MSC (listening) and STP (connect)
+init(MscLocalIP, MscLocalPort, MscRemoteIP, StpRemoteIP, StpRemotePort) ->
+	{ok, MscSock} = gen_sctp:open([{ip, MscLocalIP},{port,MscLocalPort}]
+					++ ?COMMON_SOCKOPTS),
+	io:format("Listening for MSC on ~w:~w. ~w~n",
+			[MscLocalIP, MscLocalPort, MscSock]),
+	ok = gen_sctp:listen(MscSock, true),
+	{ok, StpSock} = gen_sctp:open(?COMMON_SOCKOPTS),
+	L = #loop_data{msc_sock = MscSock, msc_local_ip = MscLocalIP, 
+			msc_remote_ip = MscRemoteIP,
+			stp_sock = StpSock, stp_remote_ip = StpRemoteIP,
+			stp_remote_port = StpRemotePort},
+	{ok, L}.
+
+% initiate a connection to STP as a client
+initiate_stp_connection(#loop_data{stp_sock = Sock, stp_remote_ip = IP, stp_remote_port = Port}, Opts) ->
+	io:format("Establishing SCTP conn to STP ~p Port ~p~n", [IP, Port]),
+	gen_sctp:connect(Sock, IP, Port, Opts ++ ?COMMON_SOCKOPTS).
+
+% main loop function
+handle_sctp(L = #loop_data{msc_sock=MscSock, msc_remote_ip=MscRemoteIp, msc_remote_port=MscRemotePort,
+		    stp_sock=StpSock, stp_remote_ip=StpRemoteIp, stp_remote_port=StpRemotePort},
+	    Sctp) ->
+	io:format("Entering receive loop ~p~n", [L]),
+	io:format("======================================================================~n"),
+	case Sctp of
+		% MSC connect or disconnect
+		{sctp, MscSock, MscRemoteIp, Port, {ANC, SAC}}
+					when is_record(SAC, sctp_assoc_change) ->
+			io:format("MSC sctp_assoc_change ~p ~p~n", [ANC, SAC]),
+			#sctp_assoc_change{state = SacState, outbound_streams = OutStreams,
+					   inbound_streams = InStreams, assoc_id = MscAssocId} = SAC,
+			case SacState of
+				comm_up ->
+					InitMsg = #sctp_initmsg{num_ostreams=InStreams,
+								max_instreams=OutStreams},
+					{ok, StpAssoc} = initiate_stp_connection(L, [{sctp_initmsg,InitMsg}]),
+					io:format("STP Assoc: ~p~n", [StpAssoc]),
+					NewL = L#loop_data{msc_remote_port = Port,
+						 msc_assoc_id = MscAssocId,
+						 stp_assoc_id = StpAssoc#sctp_assoc_change.assoc_id};
+				comm_lost ->
+					NewL = L,
+					% maybe we should simply die?
+					io:format("MSC SCTP comm_lost~n"),
+					exit(1);
+				addr_unreachable ->
+					NewL = L,
+					io:format("MSC SCTP addr_unreachable~n"),
+					% maybe we should simply die?
+					exit(1)
+			end,
+			inet:setopts(MscSock, [{active, once}]);
+		% STP connect or disconnect
+		{sctp, StpSock, StpRemoteIp, StpRemotePort, {_Anc, SAC}}
+					when is_record(SAC, sctp_assoc_change) ->
+			io:format("STP sctp_assoc_change ~p~n", [SAC]),
+			inet:setopts(StpSock, [{active, once}]),
+			NewL = L;
+		% MSC data
+		{sctp, MscSock, MscRemoteIp, MscRemotePort, {[Anc], Data}} ->
+			io:format("MSC rx data: ~p ~p~n", [Anc, Data]),
+			handle_rx_data(L, from_msc, Anc, Data),
+			inet:setopts(MscSock, [{active, once}]),
+			NewL = L;
+		% STP data
+		{sctp, StpSock, StpRemoteIp, StpRemotePort, {[Anc], Data}} ->
+			io:format("STP rx data: ~p ~p~n", [Anc, Data]),
+			handle_rx_data(L, from_stp, Anc, Data),
+			inet:setopts(StpSock, [{active, once}]),
+			NewL = L;
+		{sctp, _Sock, RemoteIp, _Remote_port, {_Anc, Data}}
+					when is_record(Data, sctp_shutdown_event) ->
+			% maybe we should simply die?
+			NewL = L,
+			io:format("SCTP remote ~p shutdown~n", [RemoteIp]),
+			exit(1);
+		Other ->
+			io:format("OTHER ~p~n", [Other]),
+			NewL = L
+	end,
+	NewL.
+
+
+try_mangle(L, From, Data) ->
+	try mgw_nat:mangle_rx_data(L, From, Data) of
+		Val ->
+			Val
+		catch error:Error ->
+			% some parser error, simply forward msg unmodified
+			io:format("MGW NAT mangling Error: ~p~n", [Error]),
+			Data
+		end.
+
+% handle incoming data on one of the SCTP sockets
+handle_rx_data(_L, From, SRInfo, Data) when is_binary(Data) ->
+	io:format("Unhandled Rx Data from SCTP from ~p: ~p, ~p~n", [From, SRInfo, Data]);
+
+handle_rx_data(L, From, SRInf = #sctp_sndrcvinfo{ppid = 2, 
+						 stream = Stream}, Data) when is_binary(Data) ->
+	DataOut = try_mangle(L, From, Data),
+	% send mangled data to other peer
+	case From of
+		from_msc ->
+			Sock = L#loop_data.stp_sock,
+			AssocId = L#loop_data.stp_assoc_id;
+		from_stp ->
+			Sock = L#loop_data.msc_sock,
+			AssocId = L#loop_data.msc_assoc_id
+	end,
+	SndRcvInfo = #sctp_sndrcvinfo{ppid = 2, stream = Stream, assoc_id = AssocId},
+	%io:format("Sending ~p to ~p ~p~n", [DataOut, Sock, SndRcvInfo]),
+	% if they are not equal, we will abort here
+	if DataOut == Data ->
+		ok;
+	   true ->
+		io:format("Data is NOT equal~n")
+	end,
+	ok = gen_sctp:send(Sock, SndRcvInfo, DataOut).
+
+