Un proxy sencillo en Erlang en un solo archivo,no mas pa practicar este lenguaje

nydus.erl

-module(nydus).
-export([test/0]).
-export([listener/1]).
-compile(debug_info).
 
test()->
	listener(3333).
listener(Port) ->
	 spawn(fun () -> {ok, Sock} = gen_tcp:listen(Port, [inet,binary,{active, false}]), 
                    mainLoop(Sock) end).

mainLoop(Sock)->
	{ok, Conn} = gen_tcp:accept(Sock),
    Handler = spawn(fun () -> handle(Conn) end),
    gen_tcp:controlling_process(Conn, Handler),
    mainLoop(Sock).

handle(Conn) ->
	{ok, Bin} = do_recv(Conn, []),
	if is_binary(Bin) ->
			{ok,ReqPayload,RemoteHost,RemotePort}=create_Request(binary_to_list(Bin)),
			{ok,SockExternalReq}=gen_tcp:connect(RemoteHost, RemotePort, [inet,
				binary,
				{packet,0},
				{active,false},
				{nodelay,true},
				{send_timeout,200},
				{recbuf,1024},
				{send_timeout_close, true}
				],2000),
			case gen_tcp:send(SockExternalReq,list_to_binary(ReqPayload)) of
				{error,timeout}->
					io:format("timeout"),
					gen_tcp:close(SockExternalReq),
					gen_tcp:close(Conn);
				{error,OtherSendError} ->
					io:format("error: ~p",[OtherSendError]),
					gen_tcp:close(SockExternalReq),
					gen_tcp:close(Conn);
				ok->
					{ok,Response}=do_recvExternalResponse(SockExternalReq,Conn,[]),
					gen_tcp:close(SockExternalReq),
					gen_tcp:close(Conn),
				_->
					io:format("otro")
			end;
		true->
			io:format("Info:~w ~n",[Bin]),
			ok=gen_tcp:send(Conn,list_to_binary("")),
			gen_tcp:close(Conn)
	end,
	ok.

create_Request(Payload)->
	RequestLines=re:split(Payload,"\r\n",[{return,list}]),
	RemoteHost=lists:nth(1,
		re:split(
			re:replace(
				lists:nth(2,
					re:split(
						lists:nth(1,RequestLines)
						," ",[{return,list}])
					),
			"http://","",[{return,list}])
		,"/",[{return,list}])
		),
	RemoteFile=re:replace(
			re:replace(
				lists:nth(1,RequestLines),
			"http://","",[{return,list}]),
		RemoteHost,"",[{return,list}]),
	%% get the server port
	Port=get_Port(RemoteHost),
	[_|NewReqLines]=RequestLines,
	ReqPayload=[RemoteFile |NewReqLines],
	{ok,string:join(ReqPayload,"\r\n"),RemoteHost,Port}.

get_Port(HostString)->
	HostParts=re:split(HostString,":",[{return,list}]),
	if length(HostParts)>1->
			string:to_integer(lists:nth(2,HostParts));
		true-> 
			80
	end.

do_recv(SockRcv, Bs) ->
    case gen_tcp:recv(SockRcv, 0) of
        {ok, B} ->
        	ReqTerminatorIsPresent=check_terminator(B),
        	Result=if ReqTerminatorIsPresent ->
        		{ok, B};
        	true->
				do_recv(SockRcv, [Bs, B])
        	end,
        	Result;
        {error, closed} ->
            {ok, Bs}
    end.

do_recvExternalResponse(SockExtResp,SockResp,Bs1)->
	case gen_tcp:recv(SockExtResp,0,1000) of
		{ok,Resp}->
			gen_tcp:send(SockResp,Resp),
			do_recvExternalResponse(SockExtResp,SockResp,[Bs1,Resp]);
		{error,closed}->
			{ok,list_to_binary(Bs1)};
		{error,timeout}->
			{ok,Bs1};
		_->
			io:format("~n ??? otra cosa.~n")
	end.

check_terminator(ReqStr)->
	%%io:format("longitud:~B~n",[LongPack]),
	%%io:format("mensaje::~s~n",[ReqStr]),
	ReqTerminator=re:run(binary_to_list(ReqStr),".*\r\n\r\n",[]),
	case ReqTerminator of
		nomatch->
			false;
		_->
			true
	end.