A library to communicate with OPC-DA servers
npm install node-opc-daThis library implements the OPC-DA specifications and allows to communicate with OPC Servers, relying on the node-dcom library for DCOM/DCE-RPC for protocol implementation. Currently this lib support browsing calls and synchronous reads. The code overall strucuture was heavly based on Utgard).
This node was created by Smart-Tech as part of the ST-One project.
Using npm:
``bash`
npm install node-opc-da
An OPC server is on object you will be using as the basis for every operation and object instantiation to communicate with a remote OPC server. Since OPC-DA relies on COM/DCOM for all it's features, to create a basic OPC Server object we'll need to create a few COM objects first.
#### Creating a Server
`javascript
// creates a COM Session from a domain, an username, and a password
let comSession = new Session();
comSession = comSession.createSession(domain, username, password);
// sets a global timeout for connections related to this session
comSession.setGlobalSocketTimeout(timeout);
// create a COM Server from a classid, an IP address and the previously created session
let comServer = new ComServer(clsid, address, comSession);
// star the COM Server
await comServer.init();
/ from the COM Server, we create a instance we'll use to create every other COM related object /
let comObject = await comServer.createInstance();
// with the comObjet created, we create an OPC Server object and call init()
let opcServer = new OPCServer();
await opcServer.init(comObject);
`
#### Removing a Server
To remove an OPC Server reference we call the `end()` function. This call only release objects created from the server object (opcBrowser, opcItemManager, opcGroupStateManager) and the server object itself. See the `node-dcom` library for more information on how to remove a COM session and server.
`javascript`
opcServer.end()
Browsing function are used to explore the items stored in the server. OPC-DA offers mainly two types of browsing: flat browsing and tree browsing. Flat Browsing returns a flat list of all server items, ignoring any internal directory tree. Tree Browsing, walks throughout the internal directory tree and returns a list of directories, each containing a list of items.
#### Flat browsing
`Javascript`
let opcBrowser = await opcServer.getBrowser();
let items = await opcBrowser.browseAllFlat();
#### Tree browsing
`Javascript`
let opcBrowser = await opcServer.getBrowser();
let items = await opcBrowser.browseAllTree();
After an OPC Server is created, if you want to read one or more items you must first create a group. To achieve this we call the function `addGroup` giving a group name and a list of options as parameters.
#### Creating a Group
`Javascript`
/* opts {
* {Boolean} [active]
* {Number} [updateRate]
* {Number} [clientHandle]
* {Number} [timeBias]
* {Number} [deadband] - until asyn read is implemented this does nothing
* {Number} [localeID]
* }
*/
let opcGroup = await opcServer.addGroup(name, opts)
#### Removing a Group
To remove a group from an opcServer we call the function `removeGroup` giving the group handle as paremeter, and a `boolean` value to indicate if the server must wait any ongoing operation to end before being removed or not.
`Javascript`
/* {Number} [handle]
* {Boolean} [force]
*/
opcServer.removeGroup(groupHandle, force);
#### Adding an Item
`javascript
// create a item manager from the group object
let opcItemManager = await opcGroup.getItemManager();
/* item {
* {String} [itemID] - the name of the item on the server, can be obtained through browser
* {Number} [clientHandle] - a locally generated number to identify this item
* }
* calls the add() function passing one or more item objects as parameter
*/
opcItemManager.add(item | itemList);
`
#### Validating an Item
`javascript`
/* item {
* {String} [itemID] - the name of the item on the server, can be obtained through browser
* {Number} [clientHandle] - a locally generated number to identify this item
* }
*/
opcItemManager.validate(item | itemList);
`javascript
// create a reading object for the group
let opcSyncIO = await opcGroup.getSyncIO();
/* {Number} [dataSource] - from where it will be read
* {Number} [serverHandles] - one or more handles. An item handle is obtained by calling
* the add() function, which returns an array of properties for each item readed.
*/
await opcSyncIO.read(dataSource, serverHandles);
``
This is a work in progress. Expect things to break, crash and burn. We cannot be hold liable for any damage to any equipment or issues directly or indirectly caused by this library. You've been warned.
This is a partial implementation and there are lots that could be done to improve what is already supported or to add support for more OPC-DA features. Feel free to dive in! Open an issue or submit PRs.