.. _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:: 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.