Socket.io - websocket connection invalid

I have a Java software that connects to Socket.io websocket, and it was working fine. Until now. My server now starts to trigger this error when I try to conect to it (Only from Java. Browsers still normal):

warn: websocket connection invalid

So, I try to create a new server with the same configs that the first one, and run the same code. Works fine. I dont know where to look to solve this.

Anyone have some clue?

Thanks very much.