[Processing net POST request] Error : Client got end of stream

My goal is to do
Arduino>Processing>Server

(> is “to”, < is “from”)

Here the server is thingworx. I am able to do, arduino>processing and by using httpie, I can simulate my programm to do processing>server.
However this last part is what cause me some issues.

You are using a websocket in your video. I was wondering if I need to create a websocket.

I am also using arduino mega like in your video.