.. _vnx.opc_ua.Proxy:

vnx.opc_ua.Proxy
================

.. cpp:namespace:: vnx::opc_ua::Proxy

Module
------

The `vnx.opc_ua.Proxy` module provides a OPC-UA proxy to connect to a OPC-UA server.

It allows to call methods as well as read variables on the server.


Options
-------

.. cpp:member:: string address
	
	OPC-UA server url to connect to, for example ``opc.tcp://127.0.0.1:4840``.
	
.. cpp:member:: string username
	
	Optional user name for server login.
	
.. cpp:member:: string password	
	
	Password for server login, required when ``username`` is set.
	
.. cpp:member:: int connect_interval_ms = 1000

	Interval to check for connection loss and reconnect. 0 to disable.

.. cpp::member:: int response_timeout_ms = 5000

	Response timeout in ms

.. cpp:member:: int session_timeout_ms = 86400000

	Session timeout in ms.

.. cpp:member:: int keepalive_interval_ms = 10000

	Connectivity check interval in ms.

.. cpp:member:: int secure_channel_lifetime_ms = 600000

	Secure channel life time in ms.

.. cpp:member:: string certificate_file = ""

	Optional path to a client certificate file (DER format).

.. cpp:member:: string private_key_file = ""

	Optional path to a client private key file (DER format).

.. cpp:member:: string application_name = "pilot.opc_ua.proxy"

	Optional application name.

.. cpp:member:: string application_uri = "urn:open62541.client.application"

	Must match the URI in the certificate.

.. cpp:member:: vector<string> trust_list

	Server certificate trust files (CRL format).
	This only has an effect if a client certificate is configured.
	If the list is empty, any certificate is accepted.

.. cpp:member:: security_mode_e security_mode = ANY

	Required security for connections.
	See :ref:`vnx.opc_ua.security_mode_e`.

.. cpp:member:: vector<subscription_t> subscriptions

	A list of subscriptions to create on connect.
	See :ref:`vnx.opc_ua.subscription_t`.

.. cpp:member:: bool block_until_connect = true
	
	If to block client requests until first sucessful connect.

.. cpp:member:: bool block_until_reconnect = false
	
	If to block client requests until next sucessful reconnect, in case connection breaks down.
	

Functions
---------

UA node ids are provided via a ``pair<ushort, Variant>``, where the first value is the namespace index
and the second value either an integer or a string.

In case a UA method returns more than one value the ``Variant`` return value
will contain an array of variants, ie. ``vector<Variant>``. See also :ref:`vnx.Variant`.

.. cpp:function:: Variant call(string method, vector<Variant> args) const
	
	Calls a global ``method`` with the given arguments and returns the result.
	The implicit object for this call is `UA_NS0ID_OBJECTSFOLDER`.
	Requires permission ``vnx.opc_ua.permission_e.CALL``.
	
.. cpp:function:: Variant object_call(pair<ushort, Variant> object, string method, vector<Variant> args) const
	
	Calls a ``method`` on the ``object`` with the given arguments and returns the result.
	Requires permission ``vnx.opc_ua.permission_e.CALL``.
	
.. cpp:function:: Variant read_variable(pair<ushort, Variant> node) const
	
	Reads the value of a given variable ``node``.
	
.. cpp:function:: Variant read_object_variable(pair<ushort, Variant> object, string variable) const
	
	Reads the value of a given ``variable`` of the ``object``.
	
.. cpp:function:: void write_variable(pair<ushort, Variant> node, Variant value)
	
	Writes a value to the given global variable ``node``.
	Requires permission ``vnx.opc_ua.permission_e.WRITE``.
	
.. cpp:function:: void write_object_variable(pair<ushort, Variant> object, string variable, Variant value)
	
	Writes a value to the given ``variable`` of the ``object``.
	Requires permission ``vnx.opc_ua.permission_e.WRITE``.
	
.. cpp:function:: void browse_all()
	
	Finds all available objects and variables on the server.
	Will be done automatically on every connect and re-connect.