org.lsst.ccs.drivers.opc

Class OPCClient

java.lang.Object

org.lsst.ccs.drivers.opc.OPCClient

public class OPCClient
extends Object

Manages a connection to an OPC DA service and fetches values from a connected server. Immutable.

The OPC DA service is assumed to be running under Windows 7 or 10, which must have its DCOM permissions and firewall configured to allow remote access to the service. The j-interop library used to communicate with the service doesn't support Kerberos, and so can't pass along existing Kerberos credentials. This requires you to provide a username and password valid on the machine running the service. SLAC policy requires that you create a local account on that machine solely for this purpose so that the password is not valid except on that machine.

Author:

tether

Constructor Summary

Constructors

Constructor and Description
OPCClient(String serverName, String domain, String classID, String username, String password) Establishes a connection to the OPC DA service.

Method Summary

Modifier and Type	Method and Description
OPCClient	close() Closes the connection to the service.
List<OPCItem>	getData() Gets the data read by the last call to readGroup().
Optional<Throwable>	getException() Gets the exception, if any, that stopped the last group read.
boolean	isOpen() Tells whether the connection to the service is still open.
OPCClient	readGroup(boolean forceUpdate) Reads all the values in the group.
OPCClient	setGroup(List<String> itemNames) Creates the group of data items to be read.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

OPCClient

public OPCClient(String serverName,
                 String domain,
                 String classID,
                 String username,
                 String password)
          throws org.lsst.ccs.drivers.commons.DriverException

Establishes a connection to the OPC DA service.

Parameters:

serverName - The hostname or IPv4 address of the server machine.

domain - The Windows domain to which the user name belongs. Must be local to the machine running the server.

classID - The class ID (CLSID) of the OPC DA service.

username - The remote username used to log in to the server.

password - The password used to log in to the server.

Throws:

org.lsst.ccs.drivers.commons.DriverException - if the connection can't be made.

Method Detail

setGroup

public OPCClient setGroup(List<String> itemNames)
                   throws org.lsst.ccs.drivers.commons.DriverException

Creates the group of data items to be read. Each addition is checked for validity with the server.

Parameters:

itemNames - A list of the item names.

Returns:

A new object whose item group contains the items specified.

Throws:

org.lsst.ccs.drivers.commons.DriverException - if the operation failed.

readGroup

public OPCClient readGroup(boolean forceUpdate)

Reads all the values in the group.

Parameters:

forceUpdate - If true causes the service to re-read each value from its device rather than returning a cached value.

Returns:

A new object that contains the data read (if any) and any exception that halted reading (if any).

getData

public List<OPCItem> getData()

Gets the data read by the last call to readGroup().

Returns:

A possibly empty list of OPCItem.

getException

public Optional<Throwable> getException()

Gets the exception, if any, that stopped the last group read.

Returns:

An Optional which if nonempty holds the exception.

isOpen

public boolean isOpen()

Tells whether the connection to the service is still open. Some reading errors may result in a closed connection.

Returns:

close

public OPCClient close()

Closes the connection to the service.

Returns:

null.