使用java简单服务器上载和下载文件

如何在这样简单的服务器上上传和下载文件，如：

public class Main {
    public static void main(String[] args) {
        try {
            ServerSocket serverSocket = new ServerSocket(9000);
            System.err.println("Visit http://localhost:" + 9000);
            while (true) {
                Socket clientSocket = serverSocket.accept();
                BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
                BufferedWriter out = new BufferedWriter(new OutputStreamWriter(clientSocket.getOutputStream()));
                String s;
                RequestParser.clear();
                while ((s = in.readLine()) != null) {
                    if (s.isEmpty()) {
                        break;
                    }
                }
                File uploadingFile = ?????????? What is $_FILE (of php) in java??
                File downloadingFile = new File("C:\\users\\myaccount\\file.pdf");
                ////how to use the file the downloading file instead of out.write?????
                //Some files are tens of megabutes and reading line by line takes much time
                out.write("<p>Its web page..</p>");
                out.close();
                in.close();
                clientSocket.close();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

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我在寻找这种解决方案中的提示，而不是像servlet或HttpServer这样的复杂工具。

那么您希望只从套接字发送和接收文件而不使用http URL吗？您需要两个独立的程序客户端和服务器端。一次将发送文件，另一次将接收文件查看JSch。。。看看这个问题：谢谢。我还找到了一些例子。一个问题是如何设置标题。该浏览器真正显示的是pdf，而不是像这样的内容：%pdf-1.4%0 obj流。。。？