封存網誌

這個網誌將不再更新，僅用於封存以前的文章，也不再提供留言功能。之前的文章我僅挑了些可能有用的出來，其他的都刪掉了。

以Erlang實作Port Mapping

最近又開始在閒暇時看Erlang的東西....
練習寫了一些簡單的東西，如這個映射TCP Port的程式 (將本地port映設到其他host的port)
例如 tcp_bridge:start("ptt.cc", 23, 1000) 後， telnet localhost:1000就會連到ptt bbs

	-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.

view raw gistfile1.erl hosted with ❤ by GitHub

其實上面的實作碼潛藏著一些問題，但是當作一個telnet的跳版已經夠用了。
這個邏輯以Erlang實作算是相當精簡的。