To get events from items, you need to add them to the session. To stop watching item state, remove it from the session. To add/remove items to/from a session, use the command core/update_data_flags:

svc=core/update_data_flags&params={"spec":[
					{
						"type":<text>,
						"data":<long|text|[long]>,
						"flags":<long>,	
						"mode":<uint>,
						"max_items":<uint>
					}
				   ]}

 You can find an example of this request in the sample Item events management.

Methods of item transmission:

• • id – by ID (if such a method is selected, you indicate item ID in the data parameter);

• • type – by type (if such a method is selected, you indicate item type in the data parameter – see Search items by property);

• col – by list of IDs (if such a method is selected, you write an array of item IDs in the data parameter).

Flags application mode:

• • 0 – redefine item flags;

• • 1 – add specified flags to those already present in the session;

• 2 – remove specified flags from the session (if you remove the base flag, the item will be removed from the session).

Flags are set to watch changes of specific item properties. The number of observed flags depend on your needs. If you want to get all events from an item, you should set up all flags. You can get events using the request avl_evts.

[		/* array of items */
	{
		"i":<long>,	/* ID  */
		"d":{		/* other fields */
			...
		},
		"f":<long>	/* applied data flags */
	},
	...
]

The format of “d” depends on item type. All formats are described in the chapter Data format.

If you call this command with flags application mode set to “2”, the field “d” will be null.