When a server calls MsgDeliverEvent() locally, it's the kernel's responsibility to deliver the event to the target thread. With the network, the server still calls MsgDeliverEvent(), but the kernel delivers a "proxy" of that event to Qnet, and it's up to Qnet to deliver the proxy to the other (client-side) Qnet, who'll then deliver the actual event to the client. Things can get screwed up on the server side, because the MsgDeliverEvent() function call is non-blocking—this means that once the server has called MsgDeliverEvent(), it's running. It's too late to turn around and say, "I hate to tell you this, but you know that MsgDeliverEvent() that I said succeeded? Well, it didn't!"