Name: mc57594 Date: 11/11/99


May be related to:
 4033357 object references are unsafe with respect to asynchronous stopping for GC
 4099926 HTTP URLConnection does not retry POST correctly
 4117685 KeepAliveStream does not get input
 4147525 bugs in HttpUrlConnection with KeepAlive

[chamness]
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When opening an HTTP connection, any additional request properties (headers) are lost, if "keep-alive" is either specified in the request or used by the Web Server. This makes it impossible to perform HTTP authentication, for example. Additionally, it slows down our system.

The two example programs demonstrate the bug. The "Sniffer" is a simple monitor program that displays the data that are going over the network. The actual client program requests a URL from the sniffer, which connects to the local web server at port 80 (I have used IIS 3.0).

Client.java:

import java.io.*;
import java.net.*;
import java.util.*;

public class Client
{
    public static void main(String[] args)
    {
        for (int i = 0; i < 5; i++)
        {
            try
            {
                URL url = new URL("http://ntsmart:6789/index.html");
                HttpURLConnection conn = (HttpURLConnection) url.openConnection();
                conn.setRequestProperty("blubber", "blabla");
// conn.setRequestProperty("Connection", "keep-alive");

                Reader in = new InputStreamReader(conn.getInputStream());
                ByteArrayOutputStream out = new ByteArrayOutputStream();
                while (true)
                {
                    int j = in.read();
                    if (j <= 0)
                    {
                        break;
                    }
                    out.write(j);
                }

                System.out.println(out.toString());

                conn.disconnect();
            }
            catch (Exception exc)
            {
                exc.printStackTrace();
            }
        }
    }
}

Sniffer.java:

import java.awt.*;
import java.io.*;
import java.net.*;

public class Sniffer extends Thread
{
    InputStream in;
    OutputStream out;
    TextArea text;
    
    public static void main(String[] args)
    {
        try
        {
            Frame f = new Frame("Sniffer");
            f.setLayout(new GridLayout(2, 1));
            TextArea clientServer = new TextArea();
            TextArea serverClient = new TextArea();
            f.add(clientServer);
            f.add(serverClient);
            f.setSize(500, 300);
            f.show();

            ServerSocket socket = new ServerSocket(6789);
            while (true)
            {
                Socket s = socket.accept();
                Socket s2 = new Socket("ntsmart", 80);
                new Sniffer(s.getInputStream(), s2.getOutputStream(), clientServer).start();
                new Sniffer(s2.getInputStream(), s.getOutputStream(), serverClient).start();
            }
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }
    }
    
    Sniffer(InputStream in, OutputStream out, TextArea text)
    {
        this.in = in;
        this.out = out;
        this.text = text;
    }
    
    public void run()
    {
        StringBuffer buffer = new StringBuffer();

        try
        {
            while (true)
            {
                int i = in.read();
                if (i <= 0)
                {
                    break;
                }
                buffer.append((char) i);
                if (i == '\n')
                {
                    text.append(buffer.toString());
                    buffer.setLength(0);
                }
                out.write(i);
            }
        }
        catch (Exception ex)
        {
            ex.printStackTrace();
        }
    }
}


Without using the "keep-alive" property, the following requests are made:

GET /index.html HTTP/1.0
blubber: blabla
  User-Agent: Java1.2.2
Host: ntsmart:6789
Accept: text/html, image/gif, image/jpeg, *; q=.2, */*; q=.2

... (and so on)

With keep alive (remove the comment from the client program) it looks like this:

GET /index.html HTTP/1.0
blubber: blabla
Connection: keep-alive
  User-Agent: Java1.2.2
Host: ntsmart:6789
Accept: text/html, image/gif, image/jpeg, *; q=.2, */*; q=.2


GET /index.html HTTP/1.0
  User-Agent: Java1.2.2
Host: ntsmart:6789
Accept: text/html, image/gif, image/jpeg, *; q=.2, */*; q=.2


GET /index.html HTTP/1.0
blubber: blabla
Connection: keep-alive
  User-Agent: Java1.2.2
Host: ntsmart:6789
Accept: text/html, image/gif, image/jpeg, *; q=.2, */*; q=.2


... (and so on)

Note, that at every second request the additional headers are missing. This also seems to close the socket, so at the 3rd request the situation is like before the first request.
(Review ID: 96018)
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