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Expand All SMB_COM_NT_CANCEL (0xA4)

This command was introduced in the NT LAN Manager dialect.

This command allows a client to request that a currently pending request be canceled. The server uses the identifiers supplied in SMB_Header to identify the client request that the client requests to cancel. The server can attempt to cancel the request or to process it immediately. The server MUST NOT send a corresponding response for this request. The client SHOULD rely on the server's response to the request that the client requests to cancel to determine the result of the request. If the server cannot identify the client's request that is to be canceled, the server SHOULD NOT send a response.<119>

This command is used primarily to cancel outstanding notify change operations initiated with the SMB_COM_NT_TRANSACT command and NT_TRANSACT_NOTIFY_CHANGE subcommand. Clients typically use NT_TRANSACT_NOTIFY_CHANGE to avoid polling for changes to directories. Other uses include canceling commands that are waiting indefinitely on a busy resource to become available or commands that retry several times for a busy resource to become available.

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