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

By default a number of notification handlers are bound for logging purposes. If you wish to remove these then you can do the following before creating any associations:

from pynetdicom import _config

# Don't bind any of the default notification handlers
_config.LOG_HANDLER_LEVEL = 'none'

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_ACTION

Service class received N-ACTION request

Handler documentation

evt.EVT_N_CREATE

Service class received N-CREATE request

Handler documentation

evt.EVT_N_DELETE

Service class received N-DELETE request

Handler documentation

evt.EVT_N_EVENT_REPORT

Service class received N-EVENT-REPORT request

Handler documentation

evt.EVT_N_GET

Service class received N-GET request

Handler documentation

evt.EVT_N_SET

Service class received N-SET request

Handler documentation

Event Handlers

Event handlers are callable functions bound to an event that get passed a single parameter, event, which is an Event instance. All Event instances come with at least three attributes:

  • Event.assoc - the Association in which the event occurred

  • Event.event - the corresponding event, as a python namedtuple

  • 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_handlers keyword argument 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.