I'm doing a project using WebSockets at the moment and I have trouble making it work. I'm not sure I fully understand the problem. So here is my attempt in explaining what happens: A tablet computer connects via WebSocket to a pharo image. On connection time a session object is created and a little later a user is associated to that session object. On login time I check if the user is already logged in to another tablet. This is by checking any session that has a user associated. So far so good. In order to make the service reliable I test it by switching on/off the flight mode of the tablet just to simulate network problems. WebSockets use TCP and the problem appears that the server does not get notice that the connection went away. At the time the client reconnects it detects that there is an active session with a user and complains about it. Handling of sessions is automatic. There are exception handlers that remove bogus sessions automatically. In order to solve the inactive session problem I do the following: If I find a session with a particular user I try to access the socket so an exception will be triggered if the connection isn't valid anymore. Theoretically it would work. When accessing the socket the exception isn't signalled in my current process but in the process that created the socket (I'm not 100% sure of this). The other process is suspended so the signalling does not occur. My second check for a session therefor sees that it is still there. But shortly after my process returns control the other process runs and removes the session from the list while handling the exception. What would be a good way to tackle this? I tried a bit using yielding the active process, resuming the other process but all doesn't feel to be quite right to solve the problem. Is there a way to let the other process run or can I have the signalled exception in my current process? Anything else? Any hints appreciated. Thanks, Norbert