Where is the Debugger or Profiler running? Flex Builder Debugger

Where is the Debugger or Profiler running? Why, localhost, I presume.....

Recently I installed Flex Builder 3 on a new machine and experienced an error when running/debugging Flex applications. What would happen is:

  • I run a Flex application
  • A popup loads asking "Where is the debugger or profiler running?"
  • I select localhost
  • The popup briefly disappears
  • The popup returns asking "Where is the debugger or profiler running?"

Another message that showed up is "A connection to the debugger or profiler could not be established by Adobe Flash Player 9"

Clicking the cancel button removed the popup and continued running the Flex application. The debugger was not working properly.

After some searching and some trial and error, I found the Flex Debugger runs on port 3434. Unblocking this port in the firewall allowed the debugger to connect on localhost.

Surprisingly, this wasn't documented very well. I hope this helps someone else. Programming in Flex without the debugger makes Homer something something...

Update The popup has come back! Oddly enough, the debugger runs now. I am very glad for that. However running any compiled Flex/AIR code brings up this silly "Where is the debugger?" popup. If anyone has an idea how to supress this, please let me know.

Update: This has been solved. Details are located here. Thank You to Shannon Hicks for giving me the solution.

13652 Views Print Print Comments (7) Flex, AIR

There are no comments for this entry.

Add Comment Subscribe to Comments

12/10/07 3:52 PM # Posted By Miles Wilson

Also having this problem.

It has started doing it on clients machines too, which is REALLY irritating.

If anyone finds a fix for this, let us know!

12/10/07 10:59 PM # Posted By Malik


I am using Flex 3 and I just started getting this as well.


12/14/07 4:17 PM # Posted By chris markiewicz

i'm now seeing this to. started happening all of a sudden. haven't found a fix yet...

12/19/07 1:56 PM # Posted By Dan Wilson


Shannon Hicks gave me the solution to this. You can find details here:



6/23/09 9:18 PM # Posted By jhay

Yes i have same problem as they i installed a adobe cs4 in my computer then everytime a go to standalone player the pop up appears i search google how to fix it they say install adobe activeX i install it already but the error pops again can anyone help me from this problem

3/31/10 2:31 PM # Posted By DM

I am a nube & also getting "where is the debugger or profiler running" after installing adobe CS3. John sez clicking terminate button will fix- I don't know where a terminate button is. Dan sez he unlocked port 3434 in firewall. I don't know how to. Is that a specific fix for Flex or will it fix this problem for this error in any Flash9? Details would be appreciated showing step-by-step procedures of unlocking this specific port in firewall (if it's the 1 I need to unlock) etc...
Thanks....you guys are great

7/14/10 10:09 PM # Posted By Ronald

though the in build debugger in flex is good enough, but I prefer using the Runtime Flex tracer in my flex projects. Its easy to use like trace. Its indeed very useful when testing applications on client machine without flash player debug versions. Any one requiring that can find it here <a href="http://askmeflash.com/applications/9/runtime-flex-...;

Add Comment Subscribe to Comments