重写common-net-ftp以适应内网Passive模式

转自 http://www.diybl.com/course/3_program/java/javajs/20100719/453294.html
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需要重写几个地方
i. org.apache.commons.net.SocketClient

/** 用来自定义 Passive 模式的 Host */
protected String _set_passive_host = "127.0.0.1";

    /**
     * Opens a Socket connected to a remote host at the specified port and
     * originating from the current host at a system assigned port.
     * Before returning, {@link #_connectAction_  _connectAction_() }
     * is called to perform connection initialization actions.
     * <p>
     * @param hostname  The name of the remote host.
     * @param port  The port to connect to on the remote host.
     * @exception SocketException If the socket timeout could not be set.
     * @exception IOException If the socket could not be opened.  In most
     *  cases you will only want to catch IOException since SocketException is
     *  derived from it.
     * @exception UnknownHostException If the hostname cannot be resolved.
     */
    public void connect(String hostname, int port)
    throws SocketException, IOException
    {
        // 将连接的hostname赋给_set_passive_host
        _set_passive_host = InetAddress.getByName(hostname).getHostAddress();
        _socket_= _socketFactory_.createSocket();
        _socket_.connect(new InetSocketAddress(hostname, port), connectTimeout);
        
        _connectAction_();
    }

ii. org.apache.commons.net.ftp.FTPClient

    private void __parsePassiveModeReply(String reply)
    throws MalformedServerReplyException
    {
        java.util.regex.Matcher m = __parms_pat.matcher(reply);
        if (!m.find()) {
            throw new MalformedServerReplyException(
                "Could not parse passive host information.\nServer Reply: " + reply);
        }
        reply = m.group();
        String parts[] = m.group().split(",");
        
        //__passiveHost = parts[0] + '.' + parts[1] + '.' + parts[2] + '.' + parts[3];
        // 此处将_set_passive_host赋给__passiveHost
        __passiveHost = _set_passive_host;
        System.out.println(">----------->> Real Host IP is : "+__passiveHost);
        try
        {
            int oct1 = Integer.parseInt(parts[4]);
            int oct2 = Integer.parseInt(parts[5]);
            __passivePort = (oct1 << 8) | oct2;
        }
        catch (NumberFormatException e)
        {
            throw new MalformedServerReplyException(
                "Could not parse passive host information.\nServer Reply: " + reply);
        }

    }