I am sorry about what I said was not detail enough. In fact, I just cut a picture from camera. I wanted to used it in another place, so the pic have to across the network to another computer. Of course, I also want to send the BufferedImage to the server side. But you know, BufferedImage is not the class that implemented the java.io.Serializable. So BufferedImage can not across the network. Maybe some class can convert it into a instance of a Output class so that I can send it by byte. but I do not know how?