OPC UA Client

logiccloud Control runtimes can act both as an OPC UA Client and Server. If you want to use logiccloud Control as OPC UA Client, add a new OPC UA Client connection.

Setting up the client connection

General Connection settings

• Connection name: name of the connection
• Connection description: description, optional
• Endpoint URL: URL of the server URL
• Security Mode: security mode used for messages; it can be one of the following: “None”, “Sign”, “SignAndEncrypt”,
• Security Policy: encryption used for messages; it can be one of the following: “None”, “Basic128Rsa15”, “Basic256”, “Basic256Sha256”, “Aes128Sha256RsaOaep”, “Aes256Sha256RsaPss”.
• Authentication: mode to authenticate to an OPC UA Server: “Anonymous”, “Credentials”, “Certificate”, “Token”.
• Application Name: the name of the client application (if empty, package name will be used for it)
• Session Name: the name of the session (if empty, server will assign a name for it)
• Session Timeout: the number of milliseconds that a session may be unused before being closed by the server
• Connect Timeout: the number of milliseconds to wait for a connection response
• Request Timeout: the number of milliseconds to wait before a ServiceRequest (i.e. Write, Publish, etc…) is cancelled
• Token lifetime: the requested number of milliseconds before a security token is renewed
• Skip server cert check: skips verification of server certificate. Skips checking HostName, Expiration, and Authority.
• Write Retry Interval: the number of milliseconds to wait before a write failed operation is retried.

Own Certificate settings

• Auto generate own certificates: If enabled, own certificate will be created automatically
• Valid Months: Validity timeframe for own certificate
• Key size: Certificate key size
• Own Certificate path: Path, where own certificate is stored
• Own Key path: Path, where own certificate key is stored

Server-client certificate settings

• Issuer Certificates Path: the file path of the issuer certificates. Issuer certificates are needed for validation, but are not trusted. Path may be to a file, comma-separated list of files, or directory.
• Issuer CRLs Paths: the file path of the issuer revocation lists. Issuer certificates are needed for validation, but are not trusted. Path may be to a file, comma-separated list of files, or directory.
• Trusted Certificates Paths: the file path of the trusted certificates. Path may be to a file, comma-separated list of files, or directory.
• Trusted CRLs Paths: the file path of the trusted revocation lists. Path may be to a file, comma-separated list of files, or directory.
• Rejected Certificates Path: the file path where rejected certificates are stored. Path must be to a directory.

Client-specific settings

• Trace requests responses: logs all low-level ServiceRequests and ServiceResponses to StdOut
• Max Buffer size: is the limit on the size of the send and receive buffers.
• Max message size: is the limit on the size of messages that may be accepted.
• Max chunk count: is the limit on the number of message chunks that may be accepted.

After adding the connection, proceed with adding a Subscription.

Creating a subscription

Subscription settings

• Subscription name: name of the subscription (the subscription contains a list of monitored items for which we will receive updates from the server)
• Priority: Indicates the relative priority of the Subscription. When more than one Subscription needs to send a Publish response, the Server should de-queue a Publish request to the Subscription with the highest priority number. For Subscriptions with equal priority the Server should de-queue Publish requests in a round-robin fashion. A Client that does not require special priority settings should set this value to zero.
• Publishing interval: This interval defines the cyclic rate that the Subscription is being requested to return Notifications to the Client. This interval is expressed in milliseconds. If the requested value is 0 or negative, the Server will revise it with the fastest supported publishing interval.
• Max notifications per publish: The maximum number of notifications that the Client wishes to receive in a single Publish response. A value of zero indicates that there is no limit.
• Max keep alive count: maximum keep-alive count. When the publishing timer has expired this number of times without requiring any NotificationMessage to be sent, the Subscription sends a keep-alive Message to the Client. If the requested value is 0, the Server will revise it with the smallest supported keep-alive count.
• Lifetime count: Requested lifetime count. The lifetime count shall be a minimum of three times the keep-alive count. When the publishing timer has expired this number of times without a Publish request being available to send a NotificationMessage, then the Subscription will be deleted by the Server.

Mapping process variables

After adding a subscription, you can map process variables.

• Variable name: Chose a variable from your POUs
• Tag browser name: non-localized human-readable name of a node when browsing the address space of the server
• Tag display name: localized human-readable name of a node when browsing the address space of the server
• Data Type: Data type of the variable
• Monitoring Mode: The monitoring mode to be set for the MonitoredItem. It can be one of the following: DISABLED (0) = The item being monitored is not sampled or evaluated, and Notifications are not generated or queued. Notification reporting is disabled. SAMPLING (1) = The item being monitored is sampled and evaluated, and Notifications are generated and queued. Notification reporting is disabled. REPORTING (2) = The item being monitored is sampled and evaluated, and Notifications are generated and queued. Notification reporting is enabled.
• Node Id: unambiguously identifies a node inside the address space of the server.
• Queue Size: The requested size of the MonitoredItem queue.
• Sampling interval: The interval that defines the fastest rate at which the MonitoredItem(s) should be accessed and evaluated. This interval is defined in milliseconds. The value 0 indicates that the Server should use the fastest practical rate. The value -1 indicates that the default sampling interval defined by the publishing interval of the Subscription is requested. A different sampling interval is used if the publishing interval is not a supported sampling interval. Any negative number is interpreted as -1.
• Discard oldest: Specifies the discard policy when the queue is full and a new Notification is to be queued. It has the following values: true = the oldest (first) Notification in the queue is discarded. The new Notification is added to the end of the queue. false = the last Notification added to the queue gets replaced with the new Notification.