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From "Peter Warren" <tomcat.subscript...@gmail.com>
Subject multiple comet requests
Date Tue, 14 Aug 2007 21:31:02 GMT
How do you send multiple requests to the same comet servlet?

Sending multiple chunks of a single request is fine.  My problem occurs
after the client ends the chunked transaction by sending "0CRLFCRLF" to the
server.  The comet servlet correctly registers the END event.

But then the client subsequently tries to initiate a new chunked request by
sending new http headers and a new chunk.  The comet servlet receives a
BEGIN event, immediately followed by an END event.  A READ event is never
generated for the new chunk.  No ERROR events are registered either.

Sequence:
1st request
BEGIN
READ
END

2nd request
BEGIN
END - why an END event and not a READ?

Below are my test client and test comet servlet.  Any thoughts on what I'm
doing wrong?

(I apologize in advance if this is a lack of understanding of http on my
part.  I have looked at the specs and tried to follow the rules but am still
running into problems.)

Thanks,
Peter

-----

<test servlet>
import java.io.IOException;
import java.io.InputStream;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.catalina.CometEvent;
import org.apache.catalina.CometProcessor;

public class CometTestServlet extends HttpServlet implements CometProcessor
{
    private static final long serialVersionUID = 5472498184127924791L;

    public void event(CometEvent cometEvent) throws IOException,
ServletException {
        HttpServletRequest request = cometEvent.getHttpServletRequest();
        HttpServletResponse response = cometEvent.getHttpServletResponse();
        // don't want timeout events
        cometEvent.setTimeout(1000000);
        if (cometEvent.getEventType() == CometEvent.EventType.BEGIN) {
            log("Begin for session: " + request.getSession(true).getId());
        } else if (cometEvent.getEventType() == CometEvent.EventType.ERROR)
{
            log("Error for session: " + request.getSession(true).getId() +
", " + cometEvent.getEventSubType());
            cometEvent.close();
        } else if (cometEvent.getEventType() == CometEvent.EventType.END) {
            log("End for session: " + request.getSession(true).getId());
            cometEvent.close();
        } else if (cometEvent.getEventType() == CometEvent.EventType.READ) {
            log("Read for session: " + request.getSession(true).getId());
            respond(request, response);
        }
    }

    private void respond(HttpServletRequest request, HttpServletResponse
response) throws IOException {
        String clientMessage = read(request);

        if (clientMessage != null && clientMessage.length() > 0) {
            response.getWriter().print(clientMessage);
            response.getWriter().flush();
        }
    }

    private String read(HttpServletRequest request) throws IOException {
        InputStream is = request.getInputStream();
        StringBuffer inputBuffer = new StringBuffer();
        byte[] buf = new byte[512];
        while (is.available() > 0) {
            int n = is.read(buf); // can throw an IOException
            if (n > 0) {
                inputBuffer.append(new String(buf, 0, n));
                log("Read " + n + " bytes: " + new String(buf, 0, n) + " for
session: "
                        + request.getSession(true).getId());
            } else if (n < 0) {
                log("comet read error");
            }
        }
        return inputBuffer.toString();
    }
}
</test servlet>

-----

<test client>
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.Socket;

public class CometTestClient1 {

    public static final String ENCODING = "ISO-8859-1";

    private Socket socket;

    private OutputStream out;

    public static void main(String[] args) throws Exception {
        CometTestClient1 test = new CometTestClient1();
        test.test();
    }

    public CometTestClient1() throws IOException {
        initConnection();
    }

    private void initConnection() throws IOException {
        socket = new Socket("127.0.0.1", 80);
        socket.setKeepAlive(true);
        out = socket.getOutputStream();
        sendHeaders();
    }

    private void sendHeaders() throws IOException {
        println("GET /CometTest HTTP/1.1");
        println("Host: 127.0.0.1");
        println("User-Agent: test");
        println("Transfer-Encoding: chunked");
        println("Connection: keep-alive");
    }

    private void test() throws IOException {
        sendChunkedMessage();
        try {
            Thread.sleep(60000);
        } catch (InterruptedException ie) {
            ie.printStackTrace();
        }
    // doesn't seem to matter if I create a new socket connection or not
        //initConnection();
        sendHeaders();
        sendChunkedMessage();

    }

    private void sendChunkedMessage() throws IOException {
        println();
        println("10");
        print("test data test 1");
        out.flush();

        String line = read();
        System.out.println(line);

        println();
        println("0");
        println();
        out.flush();

        line = read();
        System.out.println(line);
    }

    private void print(String chars) throws IOException {
        out.write(chars.getBytes(ENCODING));
    }

    private void println(String chars) throws IOException {
        out.write((chars + "\r\n").getBytes(ENCODING));
    }

    private void println() throws IOException {
        out.write(("\r\n").getBytes(ENCODING));
    }

    private String read() throws IOException {
        InputStream in = socket.getInputStream();
        StringBuffer inputBuffer = new StringBuffer();
        byte[] buf = new byte[512];
        do {
            int n = in.read(buf); // can throw an IOException
            if (n > 0) {
                inputBuffer.append(new String(buf, 0, n));
            } else if (n < 0) {
                return ("read error");
            }
        } while (in.available() > 0);
        return inputBuffer.toString();
    }
}
</test client>

-----

<test results>
HTTP/1.1 200 OK
Server: Apache-Coyote/1.1
Set-Cookie: JSESSIONID=775B71AFC0066AA45224A4F00309D101; Path=/
Transfer-Encoding: chunked
Date: Tue, 14 Aug 2007 20:00:49 GMT

10
test data test 1

0


HTTP/1.1 200 OK
Server: Apache-Coyote/1.1
Set-Cookie: JSESSIONID=BF0C8B7A0D27CDCA6A285F9C4C598613; Path=/
Content-Length: 0
Date: Tue, 14 Aug 2007 20:00:49 GMT


read error
</test results>

-----

connector configuration for tomcat 6.0.14 on windows xp:
<Connector port="80" protocol="org.apache.coyote.http11.Http11NioProtocol"
maxThreads="150" connectionTimeout="120000" keepAliveTimeout="300000"
maxKeepAliveRequests="-1" socket.soKeepAlive="true" acceptorThreadCount="2"
redirectPort="8443" />

-----

Catalina log registering begin, read, and end events for initial request,
followed by begin and end events for subsequent request:

Aug 14, 2007 1:02:37 PM org.apache.catalina.core.ApplicationContext log
INFO: CometTest: Begin for session: 910EA1A41AB07465D61585930564AFD0
Aug 14, 2007 1:02:37 PM org.apache.catalina.core.ApplicationContext log
INFO: CometTest: Read for session: 910EA1A41AB07465D61585930564AFD0
Aug 14, 2007 1:02:37 PM org.apache.catalina.core.ApplicationContext log
INFO: CometTest: End for session: 910EA1A41AB07465D61585930564AFD0
Aug 14, 2007 1:02:37 PM org.apache.catalina.core.ApplicationContext log
INFO: CometTest: Begin for session: 22A5A802D4A201A024939BE724A1F530
Aug 14, 2007 1:02:37 PM org.apache.catalina.core.ApplicationContext log
INFO: CometTest: End for session: 22A5A802D4A201A024939BE724A1F530

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