APEX Listener and EPG - strange behaviour

Question

Hi
For some years, I've used EPG for APEX but have struggled with performance particularly as I can have up to 150 student developers using at any one time.
I do a fair amount of work using ORDImage and have successfully developed APEX applications to upload image files and display full-size and thumbnail images.
After upgrading to APEX 4.1 (from 4.0), I decided to install APEX Listener standalone.
Before I did so I checked that my applications still worked in 4.1 and they did.
However, just installing APEX Listener but not configuring it (yet) has meant that my image display in a report using a procedure based on wpg_docload.download_file( l_ordimage_image.source.localData ) no longer works in EPG - the images are not displayed.
Configuring APEX Listener and running the same application through that DOES display the images.
So this part of the application works under APEX Listener but not under EPG.
My application also allows users to upload images from APEX_APPLICATION_FILES using standard code. Under APEX Listener after uploading, I'm left with a blank page with a wwv_flow.accept URL although the image does indeed upload. Under EPG it works as expected and I get a success confirmation.
So this part of the application works under EPG but not under APEX Listener.
Has anyone else come across different behaviour depending on the mode of connection?
Thanks
Brian
[Oracle EE 11gR2, Windows Server 2008R2, APEX 4.1, APEX Listener 1.1.3]

Answer 1

Hi Brian,
it sounds like you have both EPG and APEX Listener running on the same machine, so your problem might result from a port conflict. Note that both services use TCP port 8080 as default.
At least a port conflict would explain the strange behaviour in your case, some things working on one web server and some on the other.
Some parts of your initial post hint to that direction, e.g.
However, just installing APEX Listener but not configuring it (yet) has meant that my image display in a report using a procedure based on >wpg_docload.download_file( l_ordimage_image.source.localData ) no longer works in EPG - the images are not displayed.... because the APEX Listener only interfere with the EPG if it is at least running on the same machine as your database and furthermore, if it is unconfigured in terms of ist database connection, a port conflict might be the only way it could cause anything like that.
However, if you are sure that's not the issue, please check if you see any error in the APEX Listener's log for the following action you performed:
My application also allows users to upload images from APEX_APPLICATION_FILES using standard code. Under APEX Listener after uploading, I'm left with a blank >page with a wwv_flow.accept URL although the image does indeed uploadIf you actually see just a blank screen, something very bad must have happened and you should see some kind of stack trace there.
For further investigations, if necessary, it would be helpful to know how you deployed or started your APEX Listener and which JDK version you use.
For the moment, I still think the port conflict is my best guess.
You could avoid it by either changing the port for EPG (I'd not recommend that if you have other users still using it) or by changing the port for your APEX Listener.
-Udo