-module(tcp_bridge).
-export([start/3]).

start(IP, Port, LocalPort) ->
    {ok, ListenSocket} = gen_tcp:listen( LocalPort, [list, inet, {packet, raw}] ),
    spawn( fun() -> listen_loop(ListenSocket, IP, Port) end ).

listen_loop(ListenSocket, IP, Port) ->
    {ok, LocalSocket} = gen_tcp:accept(ListenSocket),
    {ok, RemoteSocket} = gen_tcp:connect(IP, Port, [list, inet, {packet, raw}], 3000),
    bridge(LocalSocket, RemoteSocket),
    bridge(RemoteSocket, LocalSocket),
    listen_loop(ListenSocket, IP, Port).

bridge(RecvSocket, SendSocket) ->
    Receiver = spawn(fun() -> reciever(RecvSocket, SendSocket) end),
    gen_tcp:controlling_process(RecvSocket, Receiver),
    Receiver.

reciever(RecvSocket, SendSocket) ->
    receive
        {tcp, _Socket, Data} ->
            gen_tcp:send(SendSocket, Data),
            reciever(RecvSocket, SendSocket);
        {tcp_closed, _Socket} ->
            gen_tcp:close(SendSocket);
        die ->
            gen_tcp:close(SendSocket);
        _ ->
            void
    end.