使用QT实现ftp上传和下载功能，有美观简洁的界面，重点实现通过信号槽获取上传和下载成功之后的反馈，根据反馈结果输出不同的信息，如上传失败、下载失败等信息。-Use QT realize ftp upload and download capabilities, focusing on obtaining feedback to achieve success after uploading and downloading through the signal channel, accordin