KVM crashes when reading content with HTTP "302 Found" response on N90 and 6680

[Emmanuel Raulo]

Hello
I found that a MIDlet will silently die on Nokia N90 and 6680 when trying to read the content of an HTTP "302 Found" server response.
Here is a small code showing it :

import javax.microedition.midlet.*;
import javax.microedition.io.*;
import java.io.*;
import javax.microedition.lcdui.*;

public class Test
extends MIDlet
{
  private static final String URL = "http://server.domain/your_script.php"
  
  protected void startApp() throws MIDletStateChangeException
  {
    Form f = new Form( "Test" );
    String response="";
    try {
      HttpConnection con = 
        (HttpConnection)Connector.open( URL, Connector.READ );
      InputStream in = con.openInputStream();
      InputStreamReader reader = new InputStreamReader(in);
      char content[] = new char[1024];
      int len = reader.read( content, 0, 1024 );
      reader.close();
      in.close();
      response = String.valueOf(content,0,len);
    }
    catch( IOException e ) {}
    f.append( new StringItem("Reponse : ", response, StringItem.PLAIN) );
    Display.getDisplay(this).setCurrent(f);
  }

  protected void pauseApp() {}

  protected void destroyApp(boolean arg0) throws MIDletStateChangeException{}
}

And here is the server-side PHP code to generate a HTTP 302 reply with content :

<?php
header('Location: http://www.forum.nokia.com/' );
echo 'plop';
?>

It was REALLY hard to find out why my much more complicated app kept on crashing...
Isn't that part of the HTTP standard to send a content together with a 302 reply ?

[steven2ffff]

hey, i feel your pain, 6630/6680 crashes too, n70 does not , but conenction still can not get through, any idea?

[peterblazejewicz]

hi,

shouldn't getResponseCode/getResponseMessage of HTTPConnection be used to handle that situation correctly?

regards,
Peter

[Emmanuel Raulo]

peterblazejewicz, getResponseCode() would return (int)302 and getResponseMessage() "302 Found".
What I wanted was the actual content of the HTTP reply (i.e. what comes after the reply headers).

I had the developer of the web service change his API to let the MIDlet connect but this is a workaround. Even if a 302 HTTP reply means that the content has moved to another URI specified in the Location: header, it seems to me that some content can be sent together (and actual implementations allow it, e.g. Apache 2 for the server-side and Nokia 3230 for client-side).

See http://www.w3.org/Protocols/rfc2616/...html#sec10.3.3 for info on "302 Found" HTTP reply.

[peterblazejewicz]

hi Emmanuel,

well, I was under impression (remember that I'm still learner) that correct action is to:
- bypass read headers/content routine
- close current connection
- reopen current conenction using Location header to request correct data,
it's based on sample I've used some time ago:

private HttpConnection open(String url) throws IOException {
    HttpConnection c;
    int status = -1;

    // Open the connection and check for redirects
    while (true) {
      c = (HttpConnection) Connector.open(url);

      // Get the status code,
      // causing the connection to be made
      status = c.getResponseCode();

      if ((status == HttpConnection.HTTP_TEMP_REDIRECT)
          || (status == HttpConnection.HTTP_MOVED_TEMP)
          || (status == HttpConnection.HTTP_MOVED_PERM)) {

        // Get the new location and close the connection
        url = c.getHeaderField("location");
        c.close();
      } else {
        break;
      }
    }

    // Only HTTP_OK (200) means the content is returned.
    if (status != HttpConnection.HTTP_OK) {
      c.close();
      throw new IOException("Response status not OK");
    }
    return c;
  }

and notes from MIDP docs:

302: The requested resource resides temporarily under a different URI. (Note: the name of this status code reflects the earlier publication of RFC2068, which was changed in RFC2616 from "moved temporalily" to "found". The semantics were not changed. The Location header indicates where the application should resend the request.)

that's I've learned so far but could be wrong of course,
hth,
regards,
Peter

[steven2ffff]

keep watching the thread , hope to get a way to handle 302 on s50 properly....

[Emmanuel Raulo]

Hi Peter,

I understand that a web browser should get the right URI from the Location header and open a new connection to that URI. In that case, that was not the behavior I was interested in.

The web service I wanted to connect would actually redirect me to some XHTML advanced profile content intended for a full-featured PC browser (i.e. FireFox, IE, etc), content that could not be used on a mobile phone, BUT the body of the reply would also contain a simple integer telling weither authentication had succeeded or failed and if the session cookie was valid for further use of the web service. Also the redirection URI was always the same and could not be used to guess what happened.

So I continue to think it's an implementation issue, even if I agree that the HTTP 302 return code is INTENDED to be used for temporary redirection, because the protocol is actually DESIGNED to allow other behaviors.

Regards,

Manu

[peterblazejewicz]

Hi Emmanuel,

I think I'm correct with a way we should handle redirection,
however on real device (I own 6680) that seems to be impossible as you found,

for example:

c = (HttpConnection) Connector.open(url);
            get_mainForm().append("Request url:\n");
            get_mainForm().append(url);
            status = c.getResponseCode();
            get_mainForm().append("response:\n");
            get_mainForm().append("code: "+c.getResponseMessage()+"\n");
            get_mainForm().append("message: "+c.getResponseCode()+"\n");
            if (status == HttpConnection.HTTP_MOVED_TEMP ||
                    status == HttpConnection.HTTP_MOVED_PERM ||
                    status == HttpConnection.HTTP_TEMP_REDIRECT) {
                url = c.getHeaderField("location").trim();
                get_mainForm().append("Redirecting to " + url+"\n");
                c.close();
                c = null;
                // other code goes here 
            }

everythings work fine in emulators (Suns WTK/Nokia SDKs),
but as soon as I tried that or similiar code on real device (6680 here) after calling:

url = c.getHeaderField("location").trim();

that thread is dead and frozen (midlet is responding fine and is working),
it does not throw any exception or something, just probably similiary to your finding its stuck forever (unitl midlet is closed),
I've tried with url which returns 302 status code:

String url = "http://www.s60.com/";

and as mentioned that works very fine on emulators,
can someone test that URL, it should nicely redirect to http://www.s60.com/life and it does that in emulators
I've also tried OperaMini and it nicely redirects but I'm not sure if redirection is not handled on server side in OperaMini implementation,

regards,
Peter

[steven2ffff]

Peter,
pretty sure that opera mini does the redirection on server side

[Frans Kouwenhoven]

Hi all,

Trying to get my browser code running on a 6680, I encounter the same troubles as described above.

Redirecting should provide a Location field, but as I enumerate all headers in the first response it's all empty (null)! Any emulator (not a S60) will provide the correct Location field.

Peter, as I see in your code:

url = c.getHeaderField("location").trim();

this statement will cause a NullPointerException. Is that the reason is seams to be frozen?

Do you also face this null header fields?

Regards,
Frans

[steven2ffff]

aha, seems we guys in this thread are all in browser related biz, care to share your applications? web sites maybe?

[peterblazejewicz]

hi Frans,

yes, that's correct, I've later wrote a code for test 6680 without using automatic redirection but simplyl to test response code and test header "location", its null, althouth it works correct on emulators (nokia/sun wtk),
that's the reason I guess of some issues decribed earlier,
I've simply will not use redirection at all unless I get some other devices for tests,
However I have non-latest firmware version and not sure if that is related (latest is 5.0.*.* released that year),
http://www.newlc.com/Nokia-Series-60...story,933.html
it could be a bug in api implementation or some firmware issue, not sure,

@steven
I've simply using HttpConenctions mainly for REST services research like some public apis: google/yahoo/flickr/etc (web 2 api) for client side applications without server side tier and client side parsing with either thing-xml parsers or jsr-172 parser (which my device does not support though), I think it bill be quite common way of sharing/accesing data in future

regards,
Peter

[hfoffani]

Hi.
I can confirm the problem in a Nokia 6630.
It also happens to me in the project I'm working.

In the following piece of code (all inside a loop to resolve the
redirections) the output of getHeaderField("Location") is null
when the status is 302.

       // Get the status code, causing the connection to be made
       status = connection.getResponseCode();
       log("HTTPstatus: " + status);
       if (status == HttpConnection.HTTP_TEMP_REDIRECT ||
               status == HttpConnection.HTTP_MOVED_TEMP ||
               status == HttpConnection.HTTP_MOVED_PERM) {
           // Get the new location and close the connection
           url = connection.getHeaderField("Location");
           connection.close();
           log("Redirecting to " + url);
       } else {
           // no redirect
           break;
       }

I've tried with "location" and "Location" with the same result.

Like the rest of us it works fine under the emulator.

Are there any way to get all the header fields? May be the info
is somewhere else.

-Hernán.

PS: Thanks Peter, I've followed your advise and am using
NetBeans right now.

[hfoffani]

Does this recipe apply here too?
http://discussion.forum.nokia.com/fo...ead.php?t=6196

Should we have parse response headers ourselves?
Ick!!!

I've simply will not use redirection at all unless I get some other devices for tests,

Lucky you!
The Google site I'm pointing at always redirect me.

-H.

[peterblazejewicz]

Hello Hernan,

Are there any way to get all the header fields?

here you are:

  public void run() {
        HttpConnection connection = null;
        int response = -1;
        StringBuffer buffer = new StringBuffer("");
        char lf = '\n';
        try {
            connection = (HttpConnection) Connector.open("http://www.forum.nokia.com/");
            buffer.append("host: ").append(connection.getHost()).append(lf);
            response = connection.getResponseCode();
            if(response == HttpConnection.HTTP_OK){
               buffer.append("response: 200").append(lf);
               // get headers
               int i = 0;
               String key = null;
               while((key = connection.getHeaderFieldKey(i++)) != null){
                   buffer.append("key: ").append(key).append(lf);
                   buffer.append("value: ").append(connection.getHeaderField(key)).append(lf);
               }
            }else{
               buffer.append("failure: ").append(response).append(lf);
            }
        } catch (IOException ex) {
            buffer.append("exception:").append(lf);
            buffer.append(ex.getMessage()).append(lf);
        } finally{
            if(connection != null){
                try {
                    connection.close();
                } catch (IOException ex) {}
            }
        }
        mainScreen.setString(buffer.toString());
        buffer = null;
    }

which should results in (add out.println if you prefer):

host: www.forum.nokia.com
response: 200
key: date
value: Tue, 15 Aug 2006 18:53:04 GMT
key: server
value: Apache
key: accept-ranges
value: bytes
key: set-cookie
value: ND=2; path=/
key: set-cookie
value: ND=2; path=/
key: content-type
value: text/html; charset=UTF-8
key: connection
value: close

(run via Sun 2.5 WTK Emulator)

PS: Thanks Peter, I've followed your advise and am using
NetBeans right now.

you're welcome

hth
regards,
Peter