If server A has opened a connection with server B, server B's session is ended because the communications link has been closed by a network error or by server A's program.
Server A continues operation.
If server B halts operation or in some way stops communicating with server A, this message will be displayed on server A indicating that the connection was closed suddenly by server B. A network failure can also cause this message to be displayed. If a large number of these messages occur simultaneously, check the network for failure and correct any problems.