How are Firefox and other long lived sockets terminated when I lock my session?

When I lock my session on xfce, Firefox and apps that rely on socket connections get their connections terminated. I find such behavior bizarre. I haven't been able to figure out why it happens or how it happens or how to disable it. I've tested with http/XMLHttpRequest ping and they are kept, but WebSockets go down as soon I lock the screen. Is there a reason for this behavior and how to disable?