尝试从 web 浏览器 Java 读取输入 stream 时，套接字挂起

Question

I am attempting to read an input stream from a socket provided by a web browser client. Every approach I have taken has got the same results thus far, it just hangs and I don't know why. I have tried mark() marking the read limit to what is available and still no go.

inputStream.mark(inputStream.available());

ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
byte[] buffer = new byte[1024 * 9];
int read;

while((read = inputStream.read(buffer)) > 0) {
    outputStream.write(buffer, 0, read);
}
byte[] bytes = outputStream.toByteArray();

I have also tried clientSocket.shutdownInput() to tried to fix this issue, still no good.

Here is my attempt below:

import java.io.*;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.Socket;
import java.nio.charset.StandardCharsets;

public class Server {
    public static void main(String[] args)
    {
        ServerSocket server = null;

        try {

            // Server is listening on port 3001
            server = new ServerSocket(3001, 1, InetAddress.getByName("localhost"));
            server.setReuseAddress(true);

            // running infinite loop for getting
            // client request
            while (true) {

                // socket object to receive incoming client
                // requests
                Socket client = server.accept();

                // Displaying that new client is connected
                // to Server
                System.out.println("New client connected"
                        + client.getInetAddress()
                        .getHostAddress());


                // create a new thread object
                ClientHandler clientSock
                        = new ClientHandler(client);

                // This thread will handle the client
                // separately
                new Thread(clientSock).start();

            }
        }catch (IOException e) {
            e.printStackTrace();
        }
    }

    // ClientHandler class
    private static class ClientHandler implements Runnable {

        private final Socket clientSocket;

        // Constructor
        public ClientHandler(Socket clientSocket)
        {
            this.clientSocket = clientSocket;
        }

        public void run() {


            InputStream inputStream = null;
            OutputStream clientOutput = null;
            try {

                inputStream = clientSocket.getInputStream();
                inputStream.mark(inputStream.available());

                clientSocket.shutdownInput();

                ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
                byte[] buffer = new byte[1024 * 9];
                int numRead;

                while((numRead = inputStream.read(buffer)) > 0) {
                    outputStream.write(buffer, 0, numRead);
                }

                byte[] bytes = outputStream.toByteArray();

                String payloadString = new String(bytes, StandardCharsets.UTF_8);
                System.out.println(payloadString);

                clientOutput = clientSocket.getOutputStream();
                clientOutput.write(("HTTP/1.1 \r\n" + "200 OK").getBytes());
                clientOutput.write(("ContentType: " + "text/html" + "\r\n").getBytes());
                clientOutput.write("\r\n".getBytes());
                clientOutput.write("Hello World!".getBytes());
                clientOutput.write("\r\n\r\n".getBytes());
                clientOutput.flush();
                inputStream.close();
                clientOutput.close();
                try{
                    clientSocket.close();
                }catch(Exception ex){
                    ex.printStackTrace();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

Any help would be most appreciated. Thank you.

Answer 1

browsers suggests you should toss this all in the garbage and use HTTP, because, well, browsers.

But, if you insist, there are two problems here.

1. You've made it crazy complicated.

You can take all of that code and replace it all with this simple little line:

byte[] bytes = in.readAllBytes();

That replaces the lines starting with in.mark(in.available()) (this line does nothing at all, I have no idea where you got this from. If you think it is supposed to do something specific, you might want to mention that. Because it doesn't do anything. mark is useful if you ever reset , which you aren't, and you don't need to here, hence, useless), all the way to `byte[] bytes =...;

2. sockets don't close unless sender goes out of its way to close it

Your read code (yours, or the much simpler one-liner above) reads everything until the stream closes. In your second snippet, you close it right away, which obviously doesn't work. You cannot know when to close it, the sender does this job. Evidently it's not doing it.

I advise you to adapt protocols that pre-roll sizes, so you know how much to read and aren't dependent on closing the socket just to signal that the data is sent.

For example:

byte[] sizeRaw = in.readNBytes(4);
int size = ByteBuffer.wrap(bytes).getInt();
byte[] bytes = in.readNBytes(size);

You will of course have to adjust the sending code to send the size first (as a 32-bit value, big endian). One way or another you have to look at the sending code here. Either fix it so that it closes once done, or, better yet, adjust it so it sends size first.