o6¶

o6 ¶

O6 - High-Level OPC UA Python Library

This package provides a high-level, pythonic interface to OPC UA functionality, built on top of the low-level _o6 C extension module.

Basic usage

from o6 import Client

client = Client("opc.tcp://localhost:4840") with client: value = client.read("ns=1;s=Temperature") client.write("ns=1;s=SetPoint", 25.0)

Classes¶

Client ¶

Bases: Client

High-level OPC UA client. See the client guide for more details.

Attributes¶

ns `instance-attribute` ¶

ns = Namespaces(self)

Namespace manager for the client. See the Namespaces API for details.

Example:

client = Client("opc.tcp://localhost:4840")
client.ns.append(o6.ns.di)
client.ns.load("nodesets/MyCustomTypes.xml", short_name="MyTypes")
client.connect()

After connecting, server-side namespaces that were not already loaded can be discovered through client.ns.remote.discover().

Important

All namespace registration or loading must happen before connect(). client.ns.append() and client.ns.load() are required pre-connection so that namespace index translation can be set up correctly. Attempting to add namespaces after the session is established raises RuntimeError.

root `instance-attribute` ¶

root = ObjectNode(
    ClientBackend(self), "i=84", QualifiedName(0, "Root")
)

The OPC UA Root folder node (i=84) and primary entry point for the node-style API.

objects `instance-attribute` ¶

objects = ObjectNode(
    ClientBackend(self), "i=85", QualifiedName(0, "Objects")
)

The Objects folder node (i=85); shortcut into the application-level address space.

types `instance-attribute` ¶

types = ObjectNode(
    ClientBackend(self), "i=86", QualifiedName(0, "Types")
)

The Types folder node (i=86); entry point for browsing the server's type hierarchies.

views `instance-attribute` ¶

views = ObjectNode(
    ClientBackend(self), "i=87", QualifiedName(0, "Views")
)

The Views folder node (i=87); entry point for server-defined address-space views.

loop `property` ¶

loop

The asyncio event loop used by this client. Set at construction time, not modifiable afterwards.

state `property` ¶

state

Return (channel_state, session_state, connect_status).

connected `property` ¶

connected

Test if a client has both SecureChannel and Session connected.

Functions¶

init ¶

__init__(
    endpoint_url=None,
    loop=None,
    *,
    logger=None,
    certificate=None,
    private_key=None,
    trust_list=None,
    revocation_list=None,
    security_mode=None,
    security_policy=None,
    application_uri=None,
    username=None,
    password=None
)

Create a new OPC UA client.

The constructor accepts the most commonly needed settings as keyword arguments. All remaining configuration — such as session_name, requested_session_timeout, session_locale_ids, endpoint, and any other ClientConfig property — can be set lazily on client.config before calling connect():

.. code-block:: python

client = Client("opc.tcp://localhost:4840")
client.config.session_name = "my-session"
client.config.requested_session_timeout = 60_000
client.config.session_locale_ids = ["en-US"]
client.config.endpoint = my_endpoint_description
client.config.set_username_password("user", "secret")
client.connect()

Parameters:

Name	Type	Description	Default
`endpoint_url`	`str \| None`	OPC UA endpoint to connect to, e.g. `"opc.tcp://localhost:4840"`. Can also be passed to `connect()`.	`None`
`loop`	`AbstractEventLoop \| None`	Asyncio event loop to use. Defaults to the running loop, or a newly created one if none is running.	`None`
`logger`	`Logger \| None`	Python logger used for all client-level log output. Equivalent to `client.config.logger`.	`None`
`certificate`	`str \| Path \| bytes \| None`	Client certificate as a file path (`str` / `Path`) or raw bytes (DER/PEM). Equivalent to `client.config.certificate`.	`None`
`private_key`	`str \| Path \| bytes \| None`	Private key matching certificate, as a file path or raw bytes. Equivalent to `client.config.private_key`.	`None`
`trust_list`	`list[str \| Path \| bytes] \| None`	Trusted server certificates, each as a file path or raw bytes. Equivalent to `client.config.trust_list`.	`None`
`revocation_list`	`list[str \| Path \| bytes] \| None`	Certificate revocation lists (CRL), each as a file path or raw bytes. Equivalent to `client.config.revocation_list`.	`None`
`security_mode`	`int \| None`	OPC UA message security mode (`UA_MessageSecurityMode` integer or `o6.MessageSecurityMode` enum). Equivalent to `client.config.security_mode`.	`None`
`security_policy`	`str \| None`	URI or short name of the security policy, e.g. `"Basic256Sha256"`. Equivalent to `client.config.security_policy`.	`None`
`application_uri`	`str \| None`	Application URI sent in the `ApplicationDescription`. Equivalent to `client.config.application_uri`.	`None`
`username`	`str \| None`	Username for `UserNameIdentityToken` authentication. Equivalent to calling `client.config.set_username_password(username, password)`.	`None`
`password`	`str \| None`	Password for `UserNameIdentityToken` authentication. Used together with username.	`None`

connect ¶

connect(no_session=False)

Connect to the server.

Establishes a SecureChannel and, by default, a Session. Finalizes encryption settings (certificate / key) before connecting.

If no_session is True, only the SecureChannel is opened (useful for discovery or when a session will be activated manually later).

Creates the default subscription.

Starts the background worker thread.

.. code-block:: python

# sync
client.connect()

# async
await client.connect()

Parameters:

Name	Type	Description	Default
`no_session`	`bool`	Open only the SecureChannel, skip Session creation.	`False`

disconnect ¶

disconnect(close_session=True, delete_subscriptions=True)

Disconnect from the server.

By default closes all subscriptions, ends the Session, and closes the SecureChannel, then stops the background worker thread.

Pass close_session=False to close only the SecureChannel while keeping the Session alive (e.g. for session transfer). In that case delete_subscriptions is ignored.

Safe to call when already disconnected or when the event loop is closed — returns None without raising.

.. code-block:: python

# sync
client.disconnect()

# async
await client.disconnect()

Parameters:

Name	Type	Description	Default
`close_session`	`bool`	Close the Session (and SecureChannel). When `False`, only the SecureChannel is closed.	`True`
`delete_subscriptions`	`bool`	Delete all active subscriptions before disconnecting. Ignored when `close_session` is `False`.	`True`

start_reverse_connect ¶

start_reverse_connect(port, hostnames=None)

Listen for an incoming OPC UA reverse connection from the server.

In the reverse-connect scenario the server initiates the TCP connection to the client. The client opens a listen socket on port and waits for the server to connect.

Close the connection with the standard disconnect.

.. code-block:: python

client.start_reverse_connect(port=4840, hostnames=["0.0.0.0"])
# ... use client ...
client.disconnect()

Parameters:

Name	Type	Description	Default
`port`	`int`	TCP port to listen on.	required
`hostnames`	`list[str] \| None`	Network interfaces to advertise. `None` or an empty list lets the stack decide (typically all interfaces).	`None`

activate_current_session ¶

activate_current_session()

Re-activate the session that is already associated with this client.

Sends an ActivateSession request using the client's stored identity token and credentials. Also creates the default subscription.

Typical use — session transfer, step 2 on the receiving client when the session was originally opened by this client and the SecureChannel has been renewed or re-established:

.. code-block:: python

client.connect()                  # establishes session
# ... channel re-established ...
client.activate_current_session() # re-bind session to new channel

activate_session ¶

activate_session(auth_token, server_nonce)

Activate a session that was created by another client.

Used for session transfer: client A's session is handed off to client B. Client B must first open a SecureChannel without a session (connect(no_session=True)), then call this method with the token and nonce retrieved from client A via get_session_authentication_token().

.. code-block:: python

# Client A — get transfer credentials
token, nonce = client_a.get_session_authentication_token()

# Client B — take over the session
client_b.connect(no_session=True)
client_b.activate_session(token, nonce)

Parameters:

Name	Type	Description	Default
`auth_token`	`NodeId`	Authentication token (`NodeId`) from the originating client's `get_session_authentication_token()`.	required
`server_nonce`	`bytes`	Server nonce bytes from the same call.	required

enter ¶

__enter__()

Enter the sync context manager; connect if not already connected.

Calls connect when the client is not yet connected, then returns self. __exit__ calls disconnect if the client is still connected when the block ends.

.. code-block:: python

with Client("opc.tcp://localhost:4840") as client:
    value = client.read("ns=1;s=Temperature")

exit ¶

__exit__(exc_type, exc_value, traceback)

Exit the sync context manager; disconnect if still connected.

Calls disconnect when the client is still connected. Exceptions from the with block are not suppressed. See __enter__ for full usage.

aenter `async` ¶

__aenter__()

Async counterpart of __enter__.

Same semantics — connects if not already connected and returns self — but uses await internally. __aexit__ awaits disconnect.

.. code-block:: python

async with Client("opc.tcp://localhost:4840") as client:
    value = await client.read("ns=1;s=Temperature")

aexit `async` ¶

__aexit__(exc_type, exc_value, traceback)

Exit the async context manager; disconnect if still connected.

Awaits disconnect when the client is still connected. Exceptions from the async with block are not suppressed. See __aenter__ for full usage.

getitem ¶

__getitem__(key)

Resolve a node ID to a typed Node object.

Reads NodeClass and BrowseName from the server and returns the matching Node subclass (e.g. VariableNode, ObjectNode, …).

key accepts anything that can be converted to a NodeId: a string ("ns=1;s=Temperature"), an integer (numeric node id in namespace 0), or a [NodeId][o6.NodeId] instance.

.. code-block:: python

node = client["ns=1;s=Temperature"]        # sync
node = await client["ns=1;s=Temperature"]  # async

service_find_servers ¶

service_find_servers(request)

Raw FindServers service call — discover servers known to a discovery server.

OPC UA Part 4 §5.5.2

service_find_servers_on_network ¶

service_find_servers_on_network(request)

Raw FindServersOnNetwork service call — enumerate servers registered via mDNS/LDS.

OPC UA Part 4 §5.5.3

service_get_endpoints ¶

service_get_endpoints(request)

Raw GetEndpoints service call — retrieve the endpoint descriptions of a server.

OPC UA Part 4 §5.5.4

service_add_nodes ¶

service_add_nodes(request)

Raw AddNodes service call — add one or more nodes to the address space.

OPC UA Part 4 §5.8.2

service_delete_nodes ¶

service_delete_nodes(request)

Raw DeleteNodes service call — remove one or more nodes from the address space.

OPC UA Part 4 §5.8.4

service_add_references ¶

service_add_references(request)

Raw AddReferences service call — add references between nodes.

OPC UA Part 4 §5.8.3

service_delete_references ¶

service_delete_references(request)

Raw DeleteReferences service call — remove references between nodes.

OPC UA Part 4 §5.8.5

service_browse ¶

service_browse(request)

Raw Browse service call — navigate the address space from one or more start nodes.

Returns references according to the BrowseDescription filter in the request. Use service_browse_next to continue if the response indicates more results are available.

OPC UA Part 4 §5.9.2

service_browse_next ¶

service_browse_next(request)

Raw BrowseNext service call — continue a Browse that returned a continuation point.

OPC UA Part 4 §5.9.3

service_translate_browse_paths_to_nodeids ¶

service_translate_browse_paths_to_nodeids(request)

Raw TranslateBrowsePathsToNodeIds service call — resolve browse paths to NodeIds.

OPC UA Part 4 §5.9.4

service_register_nodes ¶

service_register_nodes(request)

Raw RegisterNodes service call — obtain optimised NodeIds for repeated access.

OPC UA Part 4 §5.9.5

service_unregister_nodes ¶

service_unregister_nodes(request)

Raw UnregisterNodes service call — release NodeIds obtained via RegisterNodes.

OPC UA Part 4 §5.9.6

service_read ¶

service_read(request)

Raw Read service call — read one or more node attributes.

OPC UA Part 4 §5.11.2

service_history_read ¶

service_history_read(request)

Raw HistoryRead service call — read historical values or events from nodes.

OPC UA Part 4 §5.11.3

service_write ¶

service_write(request)

Raw Write service call — write one or more node attribute values.

OPC UA Part 4 §5.11.4

service_history_update ¶

service_history_update(request)

Raw HistoryUpdate service call — insert, replace, or delete historical data.

OPC UA Part 4 §5.11.5

service_call ¶

service_call(request)

Raw Call service call — invoke one or more OPC UA methods.

OPC UA Part 4 §5.12.2

get_remote_data_types ¶

get_remote_data_types(type_nodes=None)

Read custom StructureDefinition data types from the server.

Browses the server's DataType hierarchy (rooted at Structure, NodeId i=22) and reads the DataTypeDefinition and BrowseName attributes for every discovered node. Only nodes that carry a StructureDefinition (structs, structs-with-optional-fields, and unions) are included in the result.

Pass type_nodes to restrict the query to a specific set of DataType NodeIds instead of walking the full hierarchy. Passing an empty list returns [] immediately without contacting the server.

Each entry in the returned list is a dict with the following keys:

type_name (str) — BrowseName.name of the DataType node.
type_id (NodeId) — NodeId of the DataType node.
binary_encoding_id (NodeId) — default binary encoding NodeId (StructureDefinition.defaultEncodingId).
type_kind (DataTypeKind) — Structure, OptStruct (structure with optional fields), or Union.
members_size (int) — number of fields in the structure.

The result can be passed directly to [register_data_types][o6.register_data_types] to enable encoding/decoding of these types on the client.

Parameters:

Name	Type	Description	Default
`type_nodes`	`list[NodeIdLike] \| None`	Explicit DataType NodeIds to query. `None` (default) walks the full `Structure` subtype hierarchy.	`None`

get_endpoints ¶

get_endpoints(
    endpoint_url, *, locale_ids=None, profile_uris=None
)

Return the endpoints advertised by a server.

Sends a GetEndpoints request to endpoint_url. No active session is required — connect with connect(no_session=True) first if the client is not yet connected.

Each [EndpointDescription][o6.EndpointDescription] in the result describes one available endpoint and includes the endpoint URL, security mode, security policy URI, transport profile URI, server certificate, and the list of supported [UserTokenPolicy][o6.UserTokenPolicy] entries.

client.connect(no_session=True)
endpoints = client.get_endpoints("opc.tcp://localhost:4840")
for ep in endpoints:
    print(ep.endpoint_url, ep.security_mode, ep.security_policy_uri)

Parameters:

Name	Type	Description	Default
`endpoint_url`	`str`	URL of the server to query, e.g. `"opc.tcp://localhost:4840"`.	required
`locale_ids`	`list[str] \| None`	Preferred locales for localised strings in the response (e.g. `["en-US", "de-DE"]`). `None` returns the server's default locale.	`None`
`profile_uris`	`list[str] \| None`	Restrict the result to endpoints that match one of these transport profile URIs. `None` returns all endpoints.	`None`

find_servers ¶

find_servers(
    endpoint_url, *, server_uris=None, locale_ids=None
)

Return servers registered at a discovery server or known to a server.

Sends a FindServers request to endpoint_url. Typically called against a Local Discovery Server (LDS) at "opc.tcp://localhost:4840" to enumerate all servers registered on the host, or against any server to retrieve its own [ApplicationDescription][o6.ApplicationDescription].

No active session is required — connect(no_session=True) is sufficient.

Each [ApplicationDescription][o6.ApplicationDescription] in the result contains the application name, application URI, application type, product URI, and a list of discovery URLs that can be passed to get_endpoints.

.. code-block:: python

client.connect(no_session=True)
servers = client.find_servers("opc.tcp://localhost:4840")
for srv in servers:
    print(srv.application_uri, srv.discovery_urls)

Parameters:

Name	Type	Description	Default
`endpoint_url`	`str`	URL of the discovery server or server to query.	required
`locale_ids`	`list[str] \| None`	Preferred locales for the `ApplicationDescription.application_name` field. `None` uses the server's default locale.	`None`
`server_uris`	`list[str] \| None`	Restrict the result to servers whose `applicationUri` matches one of these strings. `None` returns all known servers.	`None`

find_servers_on_network ¶

find_servers_on_network(
    starting_record_id=0,
    max_records_to_return=0,
    server_capability_filter=None,
)

Return servers visible on the network via a Local Discovery Server (LDS).

Sends a FindServersOnNetwork request to the connected LDS. The LDS maintains a registry of servers that have announced themselves via mDNS or the RegisterServer2 service. This call is only meaningful when connected to an LDS; a regular OPC UA server will return an empty list or an error.

The result is paginated: use starting_record_id and max_records_to_return to page through large registries. The record_id field on each [ServerOnNetwork][o6.ServerOnNetwork] entry can be used as the starting_record_id for the next page.

Each [ServerOnNetwork][o6.ServerOnNetwork] entry contains the server name, discovery URL, and a list of capability strings (e.g. "DA" for Data Access, "HE" for Historical Events).

.. code-block:: python

# Fetch the first 100 servers that support Data Access
servers = client.find_servers_on_network(
    max_records_to_return=100,
    server_capability_filter=["DA"],
)

Parameters:

Name	Type	Description	Default
`starting_record_id`	`int`	Record ID to start from for pagination. `0` starts from the beginning of the registry.	`0`
`max_records_to_return`	`int`	Maximum number of entries to return. `0` lets the server decide (typically returns all entries).	`0`
`server_capability_filter`	`list[str] \| None`	Restrict the result to servers that advertise all of the given capability strings. `None` returns servers regardless of capabilities.	`None`

call ¶

call(object_id, method_id, input_args=[])

Invoke a method on a node.

Parameters:

Name	Description	Default
`object_id`	The object node id that owns the method.	required
`method_id`	The method node id to invoke.	required
`input_args`	Positional input arguments to pass to the method.	required

Returns:

Type	Description
`MaybeAwaitable[tuple[StatusCode, ...]]`	A tuple of status codes for the method outputs.

browse ¶

browse(
    target,
    *,
    direction=o6.BrowseDirection.FORWARD,
    reftype=o6.ns.ns0.reftypes.References.HierarchicalReferences,
    refsubtypes=True,
    nodeclass_mask=o6.NodeClass.UNSPECIFIED,
    result_mask=o6.BrowseResultMask(0)
)

Browse references from a node.

The method transparently follows server-issued continuation points by calling BrowseNext until all references have been collected, so the returned list is always complete even when the server splits the response into multiple batches.

Parameters:

Name	Type	Description	Default
`target`	`NodeIdLike`	The node id to browse from.	required
`direction`	`BrowseDirection`	The browse direction (forward, inverse, or both).	`...`
`reftype`	`NodeIdLike`	A reference type to filter by, or `None` for all types.	`...`
`refsubtypes`	`bool`	If `True`, include subtypes of the reference type.	`True`
`nodeclass_mask`	`NodeClass`	A node-class mask to filter the target nodes.	`...`
`result_mask`	`BrowseResultMask`	A browse result mask to customize returned fields.	`...`

Returns:

Type	Description
`MaybeAwaitable[list[ReferenceDescription]]`	A list of `ReferenceDescription` objects describing the found
`MaybeAwaitable[list[ReferenceDescription]]`	references.

history_read ¶

history_read(
    target,
    start_time,
    end_time,
    num_values_per_node=0,
    return_bounds=False,
    timestamps_to_return=o6.TimestampsToReturn.BOTH,
)

Read raw historical values for one or more nodes.

Parameters:

Name	Type	Description	Default
`target`	`NodeIdLike \| list[NodeIdLike]`	A node id or list of node ids to read history from.	required
`start_time`	`datetime`	The start time for the history interval.	required
`end_time`	`datetime`	The end time for the history interval.	required
`num_values_per_node`	`int`	Maximum number of values to return per node.	`0`
`return_bounds`	`bool`	If `True`, include boundary values at the interval edges.	`False`
`timestamps_to_return`	`TimestampsToReturn`	Which timestamps to return with each value.	`...`

Returns:

Type	Description
`Any`	Historical values or data values for the requested nodes.

history_update_insert ¶

history_update_insert(target, values)

Insert new historical values into a node's history.

Insertion fails for any timestamp that already has a value stored. Use history_update_replace to overwrite existing entries.

Parameters:

Name	Type	Description	Default
`target`	`NodeIdLike`	The node id whose history is being updated.	required
`values`	`list[DataValue]`	The historical values to insert.	required

Returns:

Type	Description
`Any`	The raw result of the history update operation.

history_update_replace ¶

history_update_replace(target, values)

Replace existing historical values for a node.

Replacement requires that a value already exists at each provided timestamp. Use history_update_insert to add new entries.

Parameters:

Name	Type	Description	Default
`target`	`NodeIdLike`	The node id whose history is being updated.	required
`values`	`list[DataValue]`	The historical values to replace existing entries with.	required

Returns:

Type	Description
`Any`	The raw result of the history update operation.

history_update_delete ¶

history_update_delete(target, start_time, end_time)

Delete historical values from a node.

Parameters:

Name	Type	Description	Default
`target`	`NodeIdLike`	The node id whose history should be deleted.	required
`start_time`	`datetime`	The start of the deletion interval.	required
`end_time`	`datetime`	The end of the deletion interval.	required

Returns:

Type	Description
`Any`	The raw result of the history delete operation.

add_variable_node ¶

add_variable_node(
    *,
    parent,
    parent_reference=o6.ns.ns0.reftypes.References.HierarchicalReferences.HasChild.Aggregates.HasComponent,
    browsename,
    requested_nodeid=None,
    attributes,
    type_definition=o6.ns.ns0.vartypes.BaseVariableType.BaseDataVariableType
)

Add a variable node to the server.

Parameters:

Name	Type	Description	Default
`parent`	`NodeIdLike`	The parent node id for the variable.	required
`browsename`	`QualifiedName \| str`	The BrowseName for the variable.	required
`attributes`	`VariableAttributes \| None`	The variable attributes.	required
`requested_nodeid`	`NodeIdLike \| None`	Optionally request a specific node id.	`None`
`parent_reference`	`NodeIdLike`	The reference type used to link the variable.	`HasComponent`
`type_definition`	`NodeIdLike`	The variable type definition node id.	`BaseDataVariableType`

Returns:

Type	Description
`MaybeAwaitable[NodeId]`	The newly created variable node id.

add_variable_type_node ¶

add_variable_type_node(
    *,
    parent,
    parent_reference=o6.ns.ns0.reftypes.References.HierarchicalReferences.HasChild.HasSubtype,
    browsename,
    requested_nodeid=None,
    attributes
)

Add a variable type node to the server.

Parameters:

Name	Type	Description	Default
`parent`	`NodeIdLike`	The parent node id for the type node.	required
`browsename`	`QualifiedName \| str`	The BrowseName for the variable type.	required
`attributes`	`VariableTypeAttributes`	The variable type attributes.	required
`requested_nodeid`	`NodeIdLike \| None`	Optionally request a specific node id.	`None`
`parent_reference`	`NodeIdLike`	The reference type used to link the type node.	`HasSubtype`

Returns:

Type	Description
`MaybeAwaitable[NodeId]`	The newly created variable type node id.

add_object_node ¶

add_object_node(
    *,
    parent,
    parent_reference=o6.ns.ns0.reftypes.References.HierarchicalReferences.HasChild.Aggregates.HasComponent,
    browsename,
    requested_nodeid=None,
    attributes,
    type_definition=o6.ns.ns0.objtypes.BaseObjectType
)

Add an object node to the server.

Parameters:

Name	Type	Description	Default
`parent`	`NodeIdLike`	The parent node id for the object.	required
`browsename`	`QualifiedName \| str`	The BrowseName for the object.	required
`attributes`	`ObjectAttributes`	The object attributes.	required
`requested_nodeid`	`NodeIdLike \| None`	Optionally request a specific node id.	`None`
`parent_reference`	`NodeIdLike`	The reference type used to link the object.	`HasComponent`
`type_definition`	`NodeIdLike`	The object type definition node id.	`BaseObjectType`

Returns:

Type	Description
`MaybeAwaitable[NodeId]`	The newly created object node id.

add_object_type_node ¶

add_object_type_node(
    *,
    parent,
    parent_reference=o6.ns.ns0.reftypes.References.HierarchicalReferences.HasChild.HasSubtype,
    browsename,
    requested_nodeid=None,
    attributes
)

Add an object type node to the server.

Parameters:

Name	Type	Description	Default
`parent`	`NodeIdLike`	The parent node id for the type.	required
`browsename`	`QualifiedName \| str`	The BrowseName for the object type.	required
`attributes`	`ObjectTypeAttributes`	The object type attributes.	required
`requested_nodeid`	`NodeIdLike \| None`	Optionally request a specific node id.	`None`
`parent_reference`	`NodeIdLike`	The reference type used to link the type node.	`HasSubtype`

Returns:

Type	Description
`MaybeAwaitable[NodeId]`	The newly created object type node id.

add_view_node ¶

add_view_node(
    *,
    parent,
    parent_reference=o6.ns.ns0.reftypes.References.HierarchicalReferences.HasChild.Aggregates.HasComponent,
    browsename,
    requested_nodeid=None,
    attributes
)

Add a view node to the server.

Parameters:

Name	Type	Description	Default
`parent`	`NodeIdLike`	The parent node id for the view.	required
`browsename`	`QualifiedName \| str`	The BrowseName for the view.	required
`attributes`	`ViewAttributes`	The view attributes.	required
`requested_nodeid`	`NodeIdLike \| None`	Optionally request a specific node id.	`None`
`parent_reference`	`NodeIdLike`	The reference type used to link the view.	`HasComponent`

Returns:

Type	Description
`MaybeAwaitable[NodeId]`	The newly created view node id.

add_reference_type_node ¶

add_reference_type_node(
    *,
    parent,
    parent_reference=o6.ns.ns0.reftypes.References.HierarchicalReferences.HasChild.HasSubtype,
    browsename,
    requested_nodeid=None,
    attributes
)

Add a reference type node to the server.

Parameters:

Name	Type	Description	Default
`parent`	`NodeIdLike`	The parent node id for the reference type.	required
`browsename`	`QualifiedName \| str`	The BrowseName for the reference type.	required
`attributes`	`ReferenceTypeAttributes`	The reference type attributes.	required
`requested_nodeid`	`NodeIdLike \| None`	Optionally request a specific node id.	`None`
`parent_reference`	`NodeIdLike`	The reference type used to link the node.	`HasSubtype`

Returns:

Type	Description
`MaybeAwaitable[NodeId]`	The newly created reference type node id.

add_data_type_node ¶

add_data_type_node(
    *,
    parent,
    parent_reference=o6.ns.ns0.reftypes.References.HierarchicalReferences.HasChild.HasSubtype,
    browsename,
    requested_nodeid=None,
    attributes
)

Add a data type node to the server.

Parameters:

Name	Type	Description	Default
`parent`	`NodeIdLike`	The parent node id for the data type.	required
`browsename`	`QualifiedName \| str`	The BrowseName for the data type.	required
`attributes`	`DataTypeAttributes`	The data type attributes.	required
`requested_nodeid`	`NodeIdLike \| None`	Optionally request a specific node id.	`None`
`parent_reference`	`NodeIdLike`	The reference type used to link the node.	`HasSubtype`

Returns:

Type	Description
`MaybeAwaitable[NodeId]`	The newly created data type node id.

add_method_node ¶

add_method_node(
    *,
    parent,
    parent_reference=o6.ns.ns0.reftypes.References.HierarchicalReferences.HasChild.Aggregates.HasComponent,
    browsename,
    requested_nodeid=None,
    attributes
)

Add a method node to the server.

Parameters:

Name	Type	Description	Default
`parent`	`NodeIdLike`	The parent node id for the method.	required
`browsename`	`QualifiedName \| str`	The BrowseName for the method.	required
`attributes`	`MethodAttributes`	The method attributes.	required
`requested_nodeid`	`NodeIdLike \| None`	Optionally request a specific node id.	`None`
`parent_reference`	`NodeIdLike`	The reference type used to link the method.	`HasComponent`

Returns:

Type	Description
`MaybeAwaitable[NodeId]`	The newly created method node id.

delete_node ¶

delete_node(nodeid, delete_target_references=True)

Delete one or more nodes from the address space.

Parameters:

Name	Type	Description	Default
`nodeid`	`NodeIdLike \| list[NodeIdLike]`	A single node id or list of node ids to delete.	required
`delete_target_references`	`bool`	If `True`, also delete references to the node targets.	`True`

Returns:

Type	Description
`MaybeAwaitable[StatusCode]`	The first non-Good `StatusCode` from the per-node results, or
`MaybeAwaitable[StatusCode]`	`StatusCode.Good` if all deletions succeeded.

add_reference ¶

add_reference(
    source,
    reftype,
    target,
    forward=True,
    target_nodeclass=o6.NodeClass.UNSPECIFIED,
    target_server_uri="",
)

Add a reference between two nodes.

Parameters:

Name	Type	Description	Default
`source`	`NodeIdLike`	The source node id for the reference.	required
`reftype`	`NodeIdLike`	The reference type id.	required
`target`	`NodeIdLike \| ExpandedNodeId`	The target node id.	required
`forward`	`bool`	If `True`, create a forward reference.	`True`
`target_nodeclass`	`NodeClass`	Optional target node class for the reference.	`...`
`target_server_uri`	`str`	Optional server uri when referencing an external node.	`''`

Returns:

Type	Description
`MaybeAwaitable[StatusCode]`	The `StatusCode` returned by the server for this reference.

delete_reference ¶

delete_reference(
    source,
    reftype,
    target,
    forward=True,
    delete_bidirectional=True,
)

Delete a reference between two nodes.

Parameters:

Name	Type	Description	Default
`source`	`NodeIdLike`	The source node id for the reference.	required
`reftype`	`NodeIdLike`	The reference type id.	required
`target`	`NodeIdLike`	The target node id.	required
`forward`	`bool`	If `True`, delete the forward reference.	`True`
`delete_bidirectional`	`bool`	If `True`, also delete the reverse reference.	`True`

Returns:

Type	Description
`MaybeAwaitable[StatusCode]`	The `StatusCode` returned by the server for this deletion.

create_subscription ¶

create_subscription(
    publishing_interval=100.0,
    lifetime_count=36000,
    max_keepalive_count=10,
    max_notifications_per_publish=10,
    publishing_enabled=True,
    *,
    on_created=None,
    on_status_change=None,
    on_deleted=None
)

Create a subscription to monitor data or events.

Parameters:

Name	Type	Description	Default
`req`		Optional raw create subscription request object.	required
`publishing_interval`	`float`	The desired publishing interval in milliseconds.	`100.0`
`lifetime_count`	`int`	The subscription lifetime count.	`36000`
`max_keepalive_count`	`int`	The maximum keepalive count.	`10`
`max_notifications_per_publish`	`int`	The maximum number of notifications per publish.	`10`
`publishing_enabled`	`bool`	Whether the subscription is initially enabled.	`True`
`on_created`	`Callable[[Subscription, CreateSubscriptionResponse], None] \| None`	Optional callback invoked with `(subscription, response)` once the server has acknowledged subscription creation.	`None`
`on_status_change`	`Callable[[Subscription, StatusChangeNotification], None] \| None`	Optional callback invoked with `(subscription, notification)` when the server publishes a `StatusChangeNotification` for this subscription.	`None`
`on_deleted`	`Callable[[Subscription], None] \| None`	Optional callback invoked with `(subscription,)` when the subscription is destroyed — explicitly via `delete()`, or implicitly on session close / disconnect.	`None`

Returns:

Type	Description
`MaybeAwaitable[Subscription]`	A `Subscription` object representing the created subscription.

monitor ¶

monitor(
    target,
    callback=None,
    sampling_interval=100.0,
    *,
    value_only=True,
    subscription=None,
    filter=None,
    monitoring_mode=o6.MonitoringMode.REPORTING,
    queue_size=1,
    discard_oldest=True,
    on_created=None,
    on_deleted=None
)

Monitor data changes on one or more nodes.

Parameters:

Name	Type	Description	Default
`target`	`NodeIdLike \| ReadValueId \| list[NodeIdLike \| ReadValueId]`	A node id, [ReadValueId][o6.ReadValueId], or list thereof to monitor.	required
`callback`	`DataChangeCallback \| None`	Optional callback invoked for each data change. If `None`, a default callback that prints `MonitoredItem {id}: {value}` to stdout is used.	`None`
`sampling_interval`	`float`	The requested sampling interval in milliseconds.	`100.0`
`value_only`	`bool`	If `True` (default), the callback receives the unwrapped value. If `False`, it receives the full [DataValue][o6.DataValue].	`True`
`subscription`	`Subscription \| None`	Optional subscription to attach the monitored items to. If `None` (default), the clients' default subscription is used.	`None`
`filter`	`DataChangeFilter \| None`	Optional [DataChangeFilter][o6.DataChangeFilter] to control triggering.	`None`
`monitoring_mode`	`MonitoringMode`	Monitoring mode for the item (default: `REPORTING`).	`...`
`queue_size`	`int`	Requested queue size (default: `1`).	`1`
`discard_oldest`	`bool`	Whether to discard the oldest entry when the queue is full (default: `True`).	`True`
`on_created`	`CreatedCallback \| None`	Optional lifecycle callback; see `MonitoredItem._data_change`.	`None`
`on_deleted`	`DeletedCallback \| None`	Optional lifecycle callback; see `MonitoredItem._data_change`.	`None`

Returns:

Type	Description
`MaybeAwaitable[MonitoredItem \| list[MonitoredItem]]`	A monitored item or list of monitored items created for the target nodes.

monitor_event ¶

monitor_event(
    nodeid,
    callback,
    filter=None,
    *,
    subscription=None,
    monitoring_mode=o6.MonitoringMode.REPORTING,
    queue_size=100,
    discard_oldest=True,
    on_created=None,
    on_deleted=None
)

Monitor events on a node.

Parameters:

Name	Type	Description	Default
`nodeid`	`NodeIdLike`	The node id to monitor for events.	required
`callback`	`EventCallback`	Callback invoked for each matching event.	required
`filter`	`EventFilter \| str \| None`	Optional event filter or filter expression string. If `None`, a default filter selecting `EventId`, `EventType`, `SourceName`, `Time`, `Message`, and `Severity` is used.	`None`
`subscription`	`Subscription \| None`	Optional subscription to attach the monitored item to. Defaults to :attr:`default_subscription`.	`None`
`monitoring_mode`	`MonitoringMode`	Monitoring mode for the item (default: `REPORTING`).	`...`
`queue_size`	`int`	Requested queue size (default: `100`).	`100`
`discard_oldest`	`bool`	Whether to discard the oldest entry when the queue is full (default: `True`).	`True`
`on_created`	`CreatedCallback \| None`	Optional lifecycle callback; see `MonitoredItem._event`.	`None`
`on_deleted`	`DeletedCallback \| None`	Optional lifecycle callback; see `MonitoredItem._event`.	`None`

Returns:

Type	Description
`MaybeAwaitable[MonitoredItem]`	The created monitored event item.

Subscription ¶

Represents an OPC UA subscription for monitoring data changes.

Functions¶

await ¶

__await__()

Allow await Subscription(...) to work.

Creating a subscription requires a server round-trip, but __init__ cannot be async. The round-trip is therefore started in __init__ and awaited here, so callers can write sub = await Subscription(...) and be sure the subscription is fully set up before proceeding.

bool ¶

__bool__()

Check if this is a valid subscription.

A deleted subscription evaluates to False. delete() cleans up the subscription on the server and client side, but cannot interfere with garbage collection of the Python object itself. Garbage collecting a deleted subscription is a noop in terms of state cleanup, but until then __bool__ indicates that the subscription is invalid.

delete ¶

delete()

Delete this subscription from the server.

Returns:

Type	Description
`MaybeAwaitable[None]`	The raw result of the delete operation.

modify ¶

modify(
    publishing_interval=None,
    lifetime_count=None,
    max_keepalive_count=None,
    max_notifications_per_publish=None,
    publishing_enabled=None,
)

Modify subscription parameters.

Parameters:

Name	Type	Description	Default
`publishing_interval`	`float \| None`	Optional new publishing interval.	`None`
`lifetime_count`	`int \| None`	Optional new lifetime count.	`None`
`max_keepalive_count`	`int \| None`	Optional new keepalive count.	`None`
`max_notifications_per_publish`	`int \| None`	Optional maximum notifications per publish.	`None`
`publishing_enabled`	`bool \| None`	Optional publishing enabled flag.	`None`

Returns:

Type	Description
`Any`	The raw result of the modify operation.

MonitoredItem ¶

Represents a monitored item within a subscription.

Functions¶

await ¶

__await__()

Allow await MonitoredItem(...) to work.

Creating a monitored item requires a server round-trip, but __init__ cannot be async. The round-trip is therefore started in __init__ and awaited here, so callers can write item = await MonitoredItem(...) and be sure the item is fully set up before proceeding.

bool ¶

__bool__()

Check if this is a valid MonitoredItem.

A deleted monitored item evaluates to False. delete() cleans up the monitored item on the server and client side, but cannot interfere with garbage collection of the Python object itself. Garbage collecting a deleted monitored item is a noop in terms of state cleanup, but until then __bool__ indicates that the monitored item is invalid.

delete ¶

delete()

Delete this monitored item from its subscription.

Returns:

Type	Description
`MaybeAwaitable[None]`	The raw result of the delete operation.

modify ¶

modify(
    sampling_interval=None,
    queue_size=None,
    discard_oldest=None,
    filter=None,
)

Modify monitored item parameters.

Parameters:

Name	Type	Description	Default
`sampling_interval`	`float \| None`	Optional new sampling interval.	`None`
`queue_size`	`int \| None`	Optional new queue size.	`None`
`discard_oldest`	`bool \| None`	Optional discard-oldest flag.	`None`
`filter`	`DataChangeFilter \| EventFilter \| str \| None`	Optional data change or event filter.	`None`

Returns:

Type	Description
`MaybeAwaitable[None]`	The raw result of the modify operation.

set_monitoring_mode ¶

set_monitoring_mode(mode)

Change the monitoring mode for this monitored item.

Parameters:

Name	Type	Description	Default
`mode`	`MonitoringMode`	The new monitoring mode.	required

Returns:

Type	Description
`MaybeAwaitable[None]`	The raw result of the operation.

set_triggering ¶

set_triggering(links_to_add=None, links_to_remove=None)

Configure triggering links for this monitored item.

Parameters:

Name	Type	Description	Default
`links_to_add`	`list[MonitoredItem] \| None`	Monitored items to add as triggered links.	`None`
`links_to_remove`	`list[MonitoredItem] \| None`	Monitored items to remove from triggered links.	`None`

Returns:

Type	Description
`MaybeAwaitable[None]`	The raw result of the operation.

Server ¶

Bases: Server

High-level OPC UA Server.

Parameters¶

port : int, optional TCP port number (default 4840). logger : logging.Logger, optional Custom logger object. loop : asyncio.AbstractEventLoop, optional Event loop used for cooperative scheduling. When provided (or when a running loop is detected), the server avoids spawning a background thread and instead schedules non-blocking iterations on the loop. If None and no running loop exists, a daemon thread is used as a fallback. certificate : str, Path, or bytes, optional Server certificate (file path or raw bytes). private_key : str, Path, or bytes, optional Server private key (file path or raw bytes). trust_list : list, optional Trusted certificates for client verification. issuer_list : list, optional Issuer certificates. revocation_list : list, optional Certificate revocation lists. secure_only : bool If True, reject unencrypted connections (default False). accept_all_certificates : bool If True, trust all client certificates (default False). application_uri : str, optional Override the default application URI.

Example¶

server = Server(port=4840) with server: ... temp = server.add_variable("Temperature", ... server.objects_node, 22.5) ... print(temp.value) 22.5

Attributes¶

objects_node `property` ¶

objects_node

The Objects folder (i=85).

types_node `property` ¶

types_node

The Types folder (i=86).

server_node `property` ¶

server_node

The Server object (i=2253).

Functions¶

add_namespace ¶

add_namespace(uri)

Register a namespace URI in the client's local namespace table and return its assigned index.

If ns.append() is used to load pre-built companion specs, all ns.append() calls must come before any manual add_namespace() calls. Pre-built Namespaces expect specific canonical indices; a manual add_namespace() beforehand would occupy a slot and cause ns.append() to raise ValueError.

Calling add_namespace() after all ns.append() calls is safe and simply appends at the next free index.

.. note:: End users should never need to call this directly — all namespace registration goes through client.ns.append().

start ¶

start()

Start the server networking layer.

The asyncio event loop handles all I/O, timers, and callbacks. When no running loop is detected (synchronous callers), a lightweight background daemon thread drives the loop instead.

stop ¶

stop()

Shut down the server.

add_reverse_connect ¶

add_reverse_connect(url, callback=None)

Register a reverse connect to a client listening at url.

The server will periodically attempt to establish a connection to the given client endpoint (e.g. opc.tcp://localhost:4841).

Parameters¶

url : str The OPC UA endpoint URL of the listening client. callback : callable, optional Called with (handle, state) on every state change.

Returns¶

int A handle that can be passed to :meth:remove_reverse_connect.

remove_reverse_connect ¶

remove_reverse_connect(handle)

Remove a reverse connect registration.

Parameters¶

handle : int The handle returned by :meth:add_reverse_connect.

add_variable ¶

add_variable(
    name,
    parent,
    value=None,
    *,
    nodeid=None,
    data_type=None,
    writable=True,
    historizing=False,
    ns=1
)

Add a variable node to the address space.

Parameters¶

name : str or LocalizedText Browse name (and display name) of the variable. parent : NodeIdLike Parent node (typically server.objects_node). value : any, optional Initial value. The OPC UA data-type is inferred automatically unless data_type is given explicitly. nodeid : NodeIdLike, optional Requested node id. None -> server assigns one. data_type : NodeIdLike, optional Explicit data type. If None, inferred from value. writable : bool Whether the variable is writable by clients (default True). historizing : bool Whether the variable supports historical data access (default False). ns : int Namespace index for the browse name (default 1).

Returns¶

VariableNode

add_object ¶

add_object(
    name,
    parent,
    *,
    nodeid=None,
    type_definition=BASE_OBJECT_TYPE,
    ns=1
)

Add an object node to the address space.

Parameters¶

name : str or LocalizedText Browse name / display name. parent : NodeIdLike Parent node. nodeid : NodeIdLike, optional Requested node id. type_definition : NodeIdLike, optional Type definition node (default: BaseObjectType i=58). ns : int Namespace index for the browse name.

Returns¶

ObjectNode

add_object_type ¶

add_object_type(
    name, parent=BASE_OBJECT_TYPE, *, nodeid=None, ns=1
)

Add an object type node.

Parameters¶

name : str or LocalizedText Browse name / display name. parent : NodeIdLike, optional Parent type node (default: BaseObjectType i=58). nodeid : NodeIdLike, optional Requested node id. ns : int Namespace index for the browse name.

Returns¶

ObjectTypeNode

add_variable_type ¶

add_variable_type(
    name,
    parent=BASE_VARIABLE_TYPE,
    *,
    data_type=NS0_DT_DOUBLE,
    value_rank=-1,
    nodeid=None,
    ns=1
)

Add a variable type node.

Parameters¶

name : str or LocalizedText Browse name / display name. parent : NodeIdLike, optional Parent type (default: BaseVariableType i=62). data_type : NodeIdLike, optional Data type (default: Double i=11). value_rank : int Value rank (default: -1 = scalar). nodeid : NodeIdLike, optional Requested node id. ns : int Namespace index for the browse name.

Returns¶

VariableTypeNode

add_method ¶

add_method(
    name,
    parent,
    callback,
    *,
    input_args=None,
    output_args=None,
    nodeid=None,
    ns=1
)

Add a method node to the address space.

Parameters¶

name : str or LocalizedText Browse name / display name. parent : NodeIdLike Parent node (typically an object node). callback : callable Python function called when a client invokes the method. Signature: callback(*inputs) -> list[output_values] input_args : list of Argument, optional Input argument descriptors. output_args : list of Argument, optional Output argument descriptors. nodeid : NodeId, optional Requested node id. ns : int Namespace index for the browse name.

Returns¶

MethodNode

add_reference ¶

add_reference(
    source, target, reference_type, *, forward=True
)

Add a reference between two nodes.

delete_node ¶

delete_node(nodeid, *, delete_references=True)

Delete a node from the address space.

call ¶

call(object_id, method_id, input_args=[])

Call a method node server-side with admin privileges.

Matches client.call() — returns (StatusCode, *output_arguments).

Parameters¶

object_id : NodeIdLike The object node that owns the method. method_id : NodeIdLike The method node to invoke. input_args : list, optional Input argument values.

Returns¶

tuple (status_code, output1, output2, ...)

read ¶

read(target, attr=o6.AttributeId.VALUE)

Read one or more node attributes from the server.

write ¶

write(target, value, attr=o6.AttributeId.VALUE)

Write one or more node attributes on the server.

If value is a :class:DataValue, it is written directly via UA_Server_writeDataValue — preserving any explicit status code and timestamps stored in the object. Otherwise behaves as before.

browse_node ¶

browse_node(nodeid, result_mask)

Browse children of a node.

translate_browse_paths ¶

translate_browse_paths(request)

Server-side translate browse paths to node ids.

read_node_info ¶

read_node_info(nodeid)

Return (node_class_int, browse_name) for a node.

find_data_type ¶

find_data_type(nodeid)

Look up a DataType by NodeId and return the Python type or metadata.

read_attribute ¶

read_attribute(nodeid, attr_id)

Read any standard attribute by its integer AttributeId.

read_object_property ¶

read_object_property(object_id, property_name)

Read an object property by BrowseName.

write_object_property ¶

write_object_property(object_id, property_name, value)

Write an object property by BrowseName.

ValueRank ¶

Bases: IntEnum

Enum for the most common ValueRanks. ValueRanks >2 can also be used. They indicate an array with the given dimensions. But ValueRanks >2 don't have a shortname defined in this enum class.

AccessLevel ¶

Bases: IntFlag

Bitmask values for the AccessLevel and UserAccessLevel attributes.

WriteMask ¶

Bases: IntFlag

Bitmask values for the WriteMask and UserWriteMask attributes.

SecureChannelState ¶

Bases: IntEnum

Possible status of a SecureChannel

SessionState ¶

Bases: IntEnum

Possible status of a Session

SecurityMode ¶

Bases: IntEnum

OPC UA MessageSecurityMode.

SecurityPolicy ¶

Bases: str, Enum

OPC UA security policy URIs.

Functions¶

make_argument ¶

make_argument(
    name, data_type, *, value_rank=-1, description=""
)

Create an OPC UA Argument descriptor.

Parameters¶

name : str Argument name. data_type : NodeIdLike Data type (e.g. "i=11" for Double). value_rank : int Value rank (-1 = scalar, 1 = 1D array, ...). description : str or LocalizedText Human-readable description.

Returns¶

o6.Argument

o6¶

o6 ¶

Classes¶

Client ¶

Attributes¶

ns instance-attribute ¶

root instance-attribute ¶

objects instance-attribute ¶

types instance-attribute ¶

views instance-attribute ¶

loop property ¶

state property ¶

connected property ¶

Functions¶

__init__ ¶

connect ¶

disconnect ¶

start_reverse_connect ¶

activate_current_session ¶

activate_session ¶

__enter__ ¶

__exit__ ¶

__aenter__ async ¶

__aexit__ async ¶

__getitem__ ¶

service_find_servers ¶

service_find_servers_on_network ¶

service_get_endpoints ¶

service_add_nodes ¶

service_delete_nodes ¶

service_add_references ¶

service_delete_references ¶

service_browse ¶

service_browse_next ¶

service_translate_browse_paths_to_nodeids ¶

service_register_nodes ¶

service_unregister_nodes ¶

service_read ¶

service_history_read ¶

service_write ¶

service_history_update ¶

service_call ¶

get_remote_data_types ¶

get_endpoints ¶

find_servers ¶

find_servers_on_network ¶

call ¶

browse ¶

history_read ¶

history_update_insert ¶

history_update_replace ¶

history_update_delete ¶

add_variable_node ¶

add_variable_type_node ¶

add_object_node ¶

add_object_type_node ¶

add_view_node ¶

add_reference_type_node ¶

add_data_type_node ¶

add_method_node ¶

delete_node ¶

add_reference ¶

delete_reference ¶

create_subscription ¶

monitor ¶

monitor_event ¶

Subscription ¶

Functions¶

__await__ ¶

__bool__ ¶

delete ¶

modify ¶

MonitoredItem ¶

Functions¶

__await__ ¶

__bool__ ¶

delete ¶

modify ¶

set_monitoring_mode ¶

set_triggering ¶

ns `instance-attribute` ¶

root `instance-attribute` ¶

objects `instance-attribute` ¶

types `instance-attribute` ¶

views `instance-attribute` ¶

loop `property` ¶

state `property` ¶

connected `property` ¶

init ¶

enter ¶

exit ¶

aenter `async` ¶

aexit `async` ¶

getitem ¶

await ¶

bool ¶

await ¶

bool ¶

objects_node `property` ¶

types_node `property` ¶

server_node `property` ¶