---
title: OPC UA
slug: litmusedge/quickstart-guide/industrial-systems-connection-guide/opc-ua
description: Review the different OPC UA DeviceHub drivers and what they do. 
docTags: 
createdAt: 2022-07-04T20:49:58.000Z
---

:::hint{type="info"}
**NOTE**: If the server is running on Windows, make sure to add the Domain name to the list of local hosts. See the *Hosts File* section in [Configure DNS/NTP Servers](docId\:pGZWSr3Dtjm4dgl2x93Ab) for more information.
:::

Here are the major differences for the OPC UA Client drivers:

| **This driver**                                        | **Does this**                                                                                                                                                                                                                                                   |
| ------------------------------------------------------ | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| [DeviceHub Agent](docId\:JyCLRxdTaXknOy_XgkH-0)        | Connects to the Litmus Edge DeviceHub Agent, which forwards data from an OPC Classic (Data Access) Server.                                                                                                                                                      |
| [OPC UA Client Advanced](docId\:dymfNqY-4gQlrykF0ckey) | - Recommended driver to use to connect to an OPC UA Server.
- Has subscribe and polling modes.
- Support OPC UA Alarms and Events. See [Use the OPC UA Client Advanced driver for OPC UA Alarms & Events](docId\:ZB_zpxjmx3FEM8BkJfu5o) for more details.  |
| [OPC UA Client](docId:10tYPn86wH3boiDPtk2H7)           | * Used to subscribe data from OPC UA servers.
* Only sends a message to the broker if the value changes at the server level.
* Subscription interval is defined at the driver level and does not have a polling interval at the tag level.                      |
| [OPC UA Client Poll](docId\:YEWk8Zq65mFEJoaC3aTD-)     | - Polls the OPC UA server at regular user-defined intervals, returning the latest status from all specified nodes.
- As soon as a record is generated, the status is passed to the pipeline to avoid delays in processing.                                      |