InputStream.read（）在PrintWriter之后返回-1

Question

The server & client code below attempts to send over a file with its name:

• The client sends over the file name using a PrintWriter which flushes after println is called. After, the client sends over the file contents using common method of a while loop that reads the file until InputStream.read returns -1.
• The server reads the file name using a BufferedReader ( readLine ). After, the server reads the file contents using that same while loop.

The issue is : When the server and client programs are executed locally on the same machine (my Windows laptop) everything executes successfully. However , when the programs are executed on separate machines on the same network, the server-side InputStream.read() returns -1.

I'm not looking for an answer in code. (I've already rewritten with DataInputStream) I want to know why this is the case.

Server:

try {
        ServerSocket server = new ServerSocket(3000);
        Socket client = server.accept();
        InputStream in = client.getInputStream();
        BufferedReader printIn = new BufferedReader(new InputStreamReader(in));
        String name = printIn.readLine();
        byte[] bytes = new byte[1024*16];
        File file = new File(name);
        FileOutputStream fOut = new FileOutputStream(file);
        int count;
        while ((count = in.read(bytes, 0, bytes.length)) != -1) {
            fOut.write(bytes, 0, count);
        }
        fOut.close();
        server.close();
    } catch (IOException e) {
        e.printStackTrace();
    }

Client:

try {
        Socket client = new Socket("localhost",3000);
        OutputStream out = client.getOutputStream();
        PrintWriter printOut = new PrintWriter(out,true);
        printOut.println("old.jar");
        byte[] bytes = new byte[1024*16];
        File file = new File("old.jar");
        FileInputStream fIn = new FileInputStream(file);
        int count;
        while((count = fIn.read(bytes,0, bytes.length)) != -1) {
            out.write(bytes, 0, count);
        }
        fIn.close();
        client.close();
    } catch (IOException e) {
        e.printStackTrace();
    }

Answer 1

From the comments: "You can't mix buffered streams or readers on the same socket. The BufferedReader will read ahead and consume part of the following file data."

Therefore, when InputStream.read() is called after BufferedReader.readLine() the BufferedReader consumes the file data, and so the InputStream.read() returns -1.

As to why the code executes successfully on a local connection: The local connection likely has different packeting behavior than the remote connection .

(Credit goes to @EJP)