在伺服器中有多個網絡卡，預設的路由不是當前的ftp伺服器走的路由。

             修改ftpclinent.java 中的程式碼實現。

protected Socket _openDataConnection_(String command, String arg) throws IOException {
		if (__dataConnectionMode != ACTIVE_LOCAL_DATA_CONNECTION_MODE
				&& __dataConnectionMode != PASSIVE_LOCAL_DATA_CONNECTION_MODE) {
			return null;
		}

		final boolean isInet6Address = getRemoteAddress() instanceof Inet6Address;

		Socket socket;

		if (__dataConnectionMode == ACTIVE_LOCAL_DATA_CONNECTION_MODE) {
			// if no activePortRange was set (correctly) -> getActivePort() = 0
			// -> new ServerSocket(0) -> bind to any free local port
			ServerSocket server = _serverSocketFactory_.createServerSocket(getActivePort(), 1, getHostAddress());

			try {
				// Try EPRT only if remote server is over IPv6, if not use PORT,
				// because EPRT has no advantage over PORT on IPv4.
				// It could even have the disadvantage,
				// that EPRT will make the data connection fail, because
				// today's intelligent NAT Firewalls are able to
				// substitute IP addresses in the PORT command,
				// but might not be able to recognize the EPRT command.
				if (isInet6Address) {
					if (!FTPReply.isPositiveCompletion(eprt(getReportHostAddress(), server.getLocalPort()))) {
						return null;
					}
				} else {
					if (!FTPReply.isPositiveCompletion(port(getReportHostAddress(), server.getLocalPort()))) {
						return null;
					}
				}

				if ((__restartOffset > 0) && !restart(__restartOffset)) {
					return null;
				}

				if (!FTPReply.isPositivePreliminary(sendCommand(command, arg))) {
					return null;
				}

				// For now, let's just use the data timeout value for waiting for
				// the data connection.  It may be desirable to let this be a
				// separately configurable value.  In any case, we really want
				// to allow preventing the accept from blocking indefinitely.
				if (__dataTimeout >= 0) {
					server.setSoTimeout(__dataTimeout);
				}
				socket = server.accept();
			} finally {
				server.close();
			}
		} else { // We must be in PASSIVE_LOCAL_DATA_CONNECTION_MODE

			// Try EPSV command first on IPv6 - and IPv4 if enabled.
			// When using IPv4 with NAT it has the advantage
			// to work with more rare configurations.
			// E.g. if FTP server has a static PASV address (external network)
			// and the client is coming from another internal network.
			// In that case the data connection after PASV command would fail,
			// while EPSV would make the client succeed by taking just the port.
			boolean attemptEPSV = isUseEPSVwithIPv4() || isInet6Address;
			if (attemptEPSV && epsv() == FTPReply.ENTERING_EPSV_MODE) {
				_parseExtendedPassiveModeReply(_replyLines.get(0));
			} else {
				if (isInet6Address) {
					return null; // Must use EPSV for IPV6
				}
				// If EPSV failed on IPV4, revert to PASV
				if (pasv() != FTPReply.ENTERING_PASSIVE_MODE) {
					return null;
				}
				_parsePassiveModeReply(_replyLines.get(0));
			}

			socket = _socketFactory_.createSocket();
			// 新增加bind 源地址操作。
			if (localAddr != null) {
				System.out.println(">>>>>>>>>>>>>>>>>>FTPClient localAddr"+localAddr); 
				socket.bind(new InetSocketAddress(localAddr, localPort));
			}
 

			socket.connect(new InetSocketAddress(__passiveHost, __passivePort), connectTimeout);
			if ((__restartOffset > 0) && !restart(__restartOffset)) {
				socket.close();
				return null;
			}

			if (!FTPReply.isPositivePreliminary(sendCommand(command, arg))) {
				socket.close();
				return null;
			}
		}

		if (__remoteVerificationEnabled && !verifyRemote(socket)) {
			socket.close();

			throw new IOException("Host attempting data connection " + socket.getInetAddress().getHostAddress()
					+ " is not same as server " + getRemoteAddress().getHostAddress());
		}

		if (__dataTimeout >= 0) {
			socket.setSoTimeout(__dataTimeout);
		}

		return socket;
	}