>>836
Java なり．

import java.net.*;import java.io.*;class P extends Thread{public void run(){try{
for(int d;(d=i.read())!=-1;)o.write(d);i.close();o.close();}catch(Exception e){}
}P(InputStream I,OutputStream O){i=I;o=O;}public static void main(final String[]
a)throws Exception{ServerSocket s=new ServerSocket(a.length>2?Integer.parseInt(a
[2]):8080);for(;;){Socket n=s.accept(),o=new Socket(a[0],Integer.parseInt(a[1]))
;new P(o.getInputStream(),n.getOutputStream()).start();new P(n.getInputStream(),
o.getOutputStream()).start();}}OutputStream o;InputStream i;}

改良版．
> java P host port [local port]
なり．