Events¶

pynetdicom uses an event-handler system to give the user access to the data exchanged between different services within an AE as well as the PDUs and data sent between the local and peer AEs. Two different types of events are used: notification events and intervention events. Events are imported using from pynetdicom import evt.

Notification Events¶

Notification events are those events where bound event handlers don’t need to return or yield anything (i.e. the user is notified some event has occurred). Each notification event can have multiple handlers bound to it and any exceptions raised by the handlers are caught and the exception message logged instead. The table below lists the available notification events.

Event	Description
`evt.EVT_ABORTED`	Association aborted
`evt.EVT_ACCEPTED`	Association accepted
`evt.EVT_ACSE_RECV`	ACSE received a primitive from the DUL service provider
`evt.EVT_ACSE_SENT`	ACSE sent a primitive to the DUL service provider
`evt.EVT_CONN_CLOSE`	Connection with remote closed
`evt.EVT_CONN_OPEN`	Connection with remote opened
`evt.EVT_DATA_RECV`	Data received from the peer AE
`evt.EVT_DATA_SENT`	Data sent to the peer AE
`evt.EVT_DIMSE_RECV`	DIMSE service received and decoded a message
`evt.EVT_DIMSE_SENT`	DIMSE service encoded and sent a message
`evt.EVT_ESTABLISHED`	Association established
`evt.EVT_FSM_TRANSITION`	State machine transitioning
`evt.EVT_PDU_RECV`	PDU received from the peer AE
`evt.EVT_PDU_SENT`	PDU sent to the peer AE
`evt.EVT_REJECTED`	Association rejected
`evt.EVT_RELEASED`	Association released
`evt.EVT_REQUESTED`	Association requested

Intervention Events¶

Intervention events are those events where the bound event handler must return or yield certain expected values so that pynetdicom can complete an action (i.e. user intervention is required). Each intervention event has only a single handler bound to it at all times. If the user hasn’t bound their own handler then a default will be used, which usually returns a negative response (i.e. service request failed, or extended negotiation ignored). The sole exception is the default handler for evt.EVT_C_ECHO which returns an 0x0000 Success status. The table below lists the possible intervention events.

Event	Description
Association request includes extended negotiation items
`evt.EVT_ASYNC_OPS`	Association request includes Asynchronous Operations Window negotiation item	Handler documentation
`evt.EVT_SOP_COMMON`	Association request includes SOP Class Common Extended negotiation item(s)	Handler documentation
`evt.EVT_SOP_EXTENDED`	Association request includes SOP Class Extended negotiation item(s)	Handler documentation
`evt.EVT_USER_ID`	Association request includes User Identity negotiation item	Handler documentation
Service class received a DIMSE service request
`evt.EVT_C_ECHO`	Service class received C-ECHO request	Handler documentation
`evt.EVT_C_FIND`	Service class received C-FIND request	Handler documentation
`evt.EVT_C_GET`	Service class received C-GET request	Handler documentation
`evt.EVT_C_MOVE`	Service class received C-MOVE request	Handler documentation
`evt.EVT_C_STORE`	Service class received C-STORE request	Handler documentation
`evt.EVT_N_GET`	Service class received N-GET request	Handler documentation

Event Handlers¶

All handlers bound to an event are passed a single parameter event which is an Event instance. All Event objects come with at least four attributes:

Event.assoc - the Association in which the event occurred
Event.description - a str description of the event
Event.name - the name of the event
Event.timestamp - the date and time the event occurred at (as a python datetime).

Additional attributes and properties are available depending on the event type, see the handler implementation documentation for more information.

Handlers can be bound to events through the bind(event, handler) methods in the Association and AssociationServer classes or by using the evt_handler keyword parameter to AE.associate() and AE.start_server(). Handlers can be unbound with the unbind(event, handler) methods in the Association and AssociationServer classes. See the Association guide for more details.