Network security services NMI initialization and termination messages

When a network management application successfully connects to the interface, the server sends an initialization message (a message with type NMsec_INIT) to the client. This message contains no records, but the return code and reason code are 0 to indicate successful connection completion.

When the server closes the connection (the connection can close as a result of an error, NSSD terminating, or the application's closing of the socket), the server attempts to send a termination message (a message with type NMsec_TERM) to the client. This message contains no records, but the return code and reason code indicate the cause of the connection's termination.