B4J Question [SOLVED] Update Picture with Websockets

I need to update an picture in my webapp

The server generate every 1s a new picture with the same Name, now i update the picture with

this work once. i think because the browser cache the pic.png and use this instead of the new one.
Is it possible to tell the browser to use the new pic?

i tried to name the file with a random number and delete the old one. but this need a huge number to never get the same picname.

im also tried to disable the cache with
but this has no effect