问FTP站点可以工作，但我无法从Java程序连接。我得到了java.net.UnknownHostException

EN

public void uploadFile(String fileName) throws Exception {
        FileTransferClient ftpClient = null;

        try {
            ftpClient = new FileTransferClient();
            ftpClient.setRemoteHost(gv.ftpHost);
            ftpClient.setRemotePort(21);
            ftpClient.setUserName(gv.ftpUserName);
            ftpClient.setPassword(gv.ftpPassword);
            ftpClient.getAdvancedFTPSettings().setConnectMode(FTPConnectMode.PASV);
            ftpClient.connect();

            ftpClient.uploadFile(gv.irp + fileName, fileName, WriteMode.OVERWRITE);
        }
        catch (Exception e) {
            throw new Exception("Error occured in uploadFile()\n" + e);
        }
        finally {
            if (ftpClient != null) {
                if (ftpClient.isConnected()) {
                    ftpClient.disconnect();
                }
                ftpClient = null;
            }
        }
    }