Java Http代理无法正常工作

Question

I try to implement a Java Proxy for Http (Https will be the extension after Http works). I found a lot of resources on the Internet and try to solve all problems on my own so far. But now I come to a point where I stuck. My Proxoy does not load the full http websites. I get a lot of error messages with the socket is already closed. So I think I try to send something over a Socket that is closed.

My Problem is now. I can not see why it is like this. I think a lot over the problem but I can not find the mistake. From my side The Sockets only get closed when the server close the connection to my Proxy Server. This happen when I read a -1 on the input stream from the server.

I would be happy for any help :-)

greetings Christoph

public class ProxyThread extends Thread {
Socket client_socket;
Socket server_socket;
boolean thread_var = true;
int buffersize = 32768;

ProxyThread(Socket s) {
    client_socket = s;
}

public void run() {
    System.out.println("Run Client Thread");
    try {
        // Read request
        final byte[] request = new byte[4096];
        byte[] response = new byte[4096];

        final InputStream in_client = client_socket.getInputStream();
        OutputStream out_client = client_socket.getOutputStream();

        in_client.read(request);
        System.out.println("---------------------- Request Info --------------------");
        System.out.println(new String(request));        

        Connection conn = new Connection(new String(request));
        System.out.println("---------------------- Connection Info --------------------");
        System.out.println("Host: " + conn.host);
        System.out.println("Port: " + conn.port);
        System.out.println("URL: " + conn.URL);
        System.out.println("Type: " + conn.type);
        System.out.println("Keep-Alive:" + conn.keep_alive);
        server_socket = new Socket(conn.URL, conn.port);
        InputStream in_server = server_socket.getInputStream();
        final OutputStream out_server = server_socket.getOutputStream();
        out_server.write(request);
        out_server.flush();

        Thread t = new Thread() {
            public void run() {
              int bytes_read;
              try {
                while ((bytes_read = in_client.read(request)) != -1) {
                      out_server.write(request, 0, bytes_read);
                      out_server.flush();
                }
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            }
          };
          t.start();

        int bytes_read;
        while ((bytes_read = in_server.read(response)) != -1) {
            out_client.write(response, 0, bytes_read);
            out_client.flush();
            //System.out.println("---------------------- Respone Info --------------------");
            //System.out.println(new String(response));
        }

        //System.out.println("EIGENTLICH FERTIG");
    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        try {
            client_socket.close();
            server_socket.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}
}

EDIT: My HTTP Proxy now works. The Answer is pretty helpfull once you understand what is ryl going on. If you come hear to find a solution this questions may help you:

• Does the client send a request only to one Website / Webserver? Means do we always have the same port / hostname?

• The Loop from the answer is very usefull but think where to place it?

Last think: Thanks @EJP its working your reply was very usefull. It only tooks a time to understand it!

Answer 1

You are making all the usual mistakes, and a few more.

1. The entire request is not guaranteed to arrive in a single read. You can't assume more than a single byte has arrived. You have to loop.

2. You aren't checking for end of stream at this stage.

3. You need a good knowledge of RFC 2616 to implement HTTP, specifically the parts about Content-length and transfer encoding.

4. You cannot assume that the server will close the connection after sending the response.

5. Closing either the input or the output stream or a socket closes the socket. This is the reason for your SocketException: socket closed .

6. When you get to HTTPS you will need to look at the CONNECT verb.

7. Flushing a socket output stream does nothing, and flushing inside a loop is to be avoided,