java - 通过 java 套接字发送文件详细信息失败

Question

下面的代码是更大尝试的一部分；它尝试在服务器和客户端之间传输文件的详细信息，但惨败。服务器向套接字写入 3 个元素，客户端应该接收相同的 3 个元素。客户端在读取第一个元素后阻塞。我做错了什么？!？

public class SocketIssues {

    static void client() throws Exception {

        new Thread() {

            @Override
            public void run() {

                try {
                    Thread.sleep(1000); // enough time for server to open its socket
                    Socket s = new Socket("localhost", 50001);

                    final DataInputStream dis = new DataInputStream(s.getInputStream());
                    final BufferedReader in = new BufferedReader(new InputStreamReader(dis));
                    System.out.println("CLIENT STARTED");
                    System.out.println("Operation: " + in.readLine());
                    System.out.println("Length: " + dis.readLong());
                    System.out.println("Name: " + dis.readUTF());
                } catch (Exception e) {
                    e.printStackTrace();
                }

            }

        }.start();

    }

    static void server() throws Exception {

        ServerSocket ss = new ServerSocket(50001);
        Socket s = ss.accept();
        System.out.println("SERVER: client connected");
        DataOutputStream dos = new DataOutputStream(s.getOutputStream());
        BufferedWriter out = new BufferedWriter(new OutputStreamWriter(dos));
        long l = 2194;
        String nume = "The file name";

        out.write("FILE1" + System.lineSeparator());
        out.flush();
        dos.writeLong(l);
        dos.flush();
        dos.writeUTF(nume);
        dos.flush();
        System.out.println("SERVER: done sending" + System.lineSeparator());
    }

    public static void main(String[] args) throws Exception {
        client();
        server();

    }
}

Answer 1

尝试仅使用DataOutputStream，而不是在数据和缓冲写入器之间混合它们，并使用读/写 UTF() 方法，就像您已经对最后一个对象所做的那样:

    DataOutputStream dos = new DataOutputStream(s.getOutputStream());
    long l = 2194;
    String nume = "The file name";

    dos.writeUTF("FILE1");
    dos.flush();
    dos.writeLong(l);
    dos.flush();
    dos.writeUTF(nume);
    dos.flush();
    System.out.println("SERVER: fisier trimis" + System.lineSeparator());

然后在客户端:

                final DataInputStream dis = new DataInputStream(s.getInputStream());
                System.out.println("CLIENT STARTED");
                System.out.println("Operation: " + dis.readUTF());
                System.out.println("Length: " + dis.readLong());
                System.out.println("Name: " + dis.readUTF());

本质上，有两层缓冲正在进行。当您从 BufferedReader 调用 readLine() 时，它可能会继续从底层流中窃取更多字节，因为这就是它应该做的事情。然后，当您返回 DataInputStream 并尝试读取对象时，前导码消失了(BufferedReader 窃取了它)，并且它将阻塞等待它，即使流中有字节。