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.

Association related¶

Event	Description
`evt.EVT_ASYNC_OPS`	Association request includes asynchronous operations negotiation item
`evt.EVT_SOP_COMMON`	Association request includes SOP Class Common Extended negotiation item(s)
`evt.EVT_SOP_EXTENDED`	Association request includes SOP Class Extended negotiation item(s)
`evt.EVT_USER_ID`	Association request includes User Identity negotiation item

Service Class related¶

Event	Description
`evt.EVT_C_ECHO`	Received C-ECHO request
`evt.EVT_C_FIND`	Received C-FIND request
`evt.EVT_C_GET`	Received C-GET request
`evt.EVT_C_MOVE`	Received C-MOVE request
`evt.EVT_C_STORE`	Received C-STORE request
`evt.EVT_N_ACTION`	Received N-ACTION request
`evt.EVT_N_CREATE`	Received N-CREATE request
`evt.EVT_N_DELETE`	Received N-DELETE request
`evt.EVT_N_EVENT_REPORT`	Received N-EVENT-REPORT request
`evt.EVT_N_GET`	Received N-GET request
`evt.EVT_N_SET`	Received N-SET request

Event Handlers¶

Event handlers are callable functions bound to an event that, at a minimum, 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.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 evt_handlers keyword parameter with AE.associate() and AE.start_server(). evt_handlers should be a list of 2- or 3-tuples:

from pynetdicom import evt, AE
from pynetdicom.sop_class import Verification, CTImageStorage

def handle_echo(event):
    # Because we used a 2-tuple to bind `handle_echo` we
    #   have no extra parameters
    return 0x0000

def handle_store(event, arg1, arg2):
    # Because we used a 3-tuple to bind `handle_store` we
    #   have optional extra parameters
    assert arg1 == 'optional'
    assert arg2 == 'parameters'
    return 0x0000

handlers = [
    (evt.EVT_C_ECHO, handle_echo),
    (evt.EVT_C_STORE, handle_store, ['optional', 'parameters']),
]

ae = AE()
ae.add_supported_context(Verification)
ae.add_supported_context(CTImageStorage)
ae.start_server(("127.0.0.1", 11112), evt_handlers=handlers)

If using a 3-tuple then the third item should be a list of objects that will be passed to the handler as extra parameters.

The other way to bind handlers to events is through the Association.bind() and AssociationServer.bind() methods. Handlers can be unbound with Association.unbind() and AssociationServer.unbind() methods. See the Association guide for more details.