Hi
I have written a simple MIDLet that fetches images from the server and displays it on the Mobile screen. The user is allowed to refresh the image which fetches a new image from the server. I have tested the application on a Nokia 7210, I seem to be getting horrible response time when ever each image is to be downloaded. The image that I am downloading is about 10 to
13 Kb png image.
Location: London(UK)
Mobile Network Used : O2(GPRS)
Phone : Nokia 7210.
Here is what my application code does ( I know it is a pain reading through code but I have included a lot of comments to reduce the pain)
...
// Open and HTTP Connection to the server
waitScr.setMessage("Connecting");
httpCon = (HttpConnection) Connector.open(url);
// Set up request headers
setUpConnectionRequest();
// Add the application specific headers.
httpCon.setRequestProperty(REQUEST_HEADER_DEST_IMG_MIME_TYPE,
IMG_MIME_TYPE);
httpCon.setRequestProperty(REQUEST_HEADER_IMG_SRC_URL, hImgUrl);
httpCon.setRequestProperty(REQUEST_HEADER_IMG_WIDTH, hImgWidth);
// Open the connection
waitScr.setMessage("Sending Request");
din = httpCon.openDataInputStream(); // Here is long delay
waitScr.setMessage("Got the connection");
int contentLength = (int) httpCon.getLength();
// Create the byte array for storing the data read from the server
byte[] raw = new byte[contentLength];
waitScr.setMessage("Reading data");
din.readFully(raw); // Read the data from the server.
waitScr.setMessage("Almost Done");
Image img = Image.createImage(raw, 0, raw.length);
srtCamDisplay.setImage(img);
raw = null;
// Clean up.
din.close();
httpCon.close();
din = null;
httpCon = null;
...
The code also includes the usual error checking and exception handling stuff but I have not included it.
Here is the problem that I am facing.
I have tested the application on '
Java 2 Micro Edition Toolkit' using a dial up connection to the internet. The application runs perfectly fine and I get all the differnt status messages on the mobile screen indicating the
progress. The status messages are displayed on the screen in the method waitScr.setMessage("....")
So when executing on the toolkit I get the following messages
'Sending Request'
( after about 10 - 20 sec )
'Got the Connection'
( after about 1 sec or less )
'Reading Data'
( after about 10-15 secs )
'Almost done'
After which the image is displayed on the mobile screen.
Now when I am running the same application the mobile phone - Nokia7210 ( UK Network - O2)
I just a see a single message 'Sending Request' for a variable period of time ( from 20 to 50 sec ) after which I see image on the mobile screen, I dont see any ofthe other messages like 'Reading Data' etc.
For
testing I included a short sleep time in between the differnt messages displayed on the screen, after
which I ran the application on the phone and I could all the differnt messages.
So I assume that when I run the applicaton on the real phone (with out the sleep )I am facing a long delay at the following location in the code
din = httpCon.openDataInputStream(); // Here is long delay
Since I after I get the connection to the server every thing else process really very fast so I dont see the messages following 'Sending Request'.
I have also noticed something else, whenever I am downloading an Image there should be a symbol 'G' appearing
at the top indicating the phone is accessing GRPS, at times I can see the message 'Sending Request' but I dont
see the 'G' symbol, after a while ( 10 sec ) see the 'G' symbol after which I get the image.
Since my application allows the user to refresh the image, as a result of the whcih the application makes a
new request to the server which takes the same amount of time again.
The server application which provides the images to the MIDLet is a
servlet which generates the images based on
the request. Since the MIDLet is going to download images quite frequently is there any way that I can use
keep alive http connections from the MIDlet to fetch images from the server. I assume that by using keep-alive
connections to the server(servlet) I will face the delay only initially and not every time the user wishes to
refresh the image.
Inorder to use keep alive connections I set up the 'Connection: Keep-Alive' header in the request sent to the server from
the MIDLet. But the response that I get from the server(servlet) contains the header 'Connection: close' I assume that
the servlet is closing the connection.
Does any one have an implementation of keep alive conneciton using MIDLet and Servelets.
vivek
din = httpCon.openDataInputStream(); // Here is long delay
