Parameters

General

Endpoint URL: contains the identifier of the server connection endpoint, for example: opc.tcp://localhost:43043/MonokotOPC.

Note that only binary transport profile (UA TCP) is supported, so the Endpoint URL must start with opc.tcp://

Security Policy: specifies the endpoint security policy (None, Basic128Rsa15, Basic256, Basic256Sha256).

Security Mode: specifies the endpoint security mode (None, Sign, SignAndEncrypt).

Connection Timeout: indicates timeout (in milliseconds) to discover the endpoints of OPC UA server.

Session Timeout: indicates for how many seconds a session should exist if the connection between client and server is lost. After session timeout, the server closes the session and frees all resources it occupied.

Channel Renewal Timeout: specifies the interval (in seconds) before the encryption keys are renewed.

Watchdog Interval: specifies the interval (in milliseconds) for checking the connection to the server.

Reconnect Interval: indicates delay (in milliseconds) before each new attempt to reconnect to the server, in case the connection was lost.

Request Timeout: specifies a timeout (in milliseconds) for sending/receiving data over the network.

Subscription

Publishing Interval: indicates new data publishing rate (in milliseconds).

Max. Notifications per Publish: specifies the maximum number of notifications that each data publication can contain. By default, the parameter is 0, which means the maximum possible number of publications determined by the server.

Keep Alive Count: specifies for how many publishing intervals the silence mode must be maintained before the server starts testing the connection to the client.

Lifetime Count: specifies for how many publishing intervals the silence mode must be maintained before the server terminates the subscription and frees all resources it occupies.

Subscription Priority: indicates priority for subscription. Higher number means that notifications for this subscription will be sent with higher priority.

Re-applying Changes: indicates delay (in seconds) before each new attempt to add monitored subscription items. This option is only used if, at the time the subscription is created, the server is unable to provide all the monitored items required by the client because they have not yet been created on the server.

Update Mode: indicates which data receiving mode is used:

• Exception (Notification).

• Poll.

Used Timestamp: indicates what timestamp should be used when forming the time of OPC UA client-associated tags update.

Sample Interval: specifies the rate (in milliseconds) at which the server should read values for the monitored items.

Queue Size: specifies the maximum queue size of values to be sent to the client that were read for the monitored item.

Discard Oldest: indicates which values (newest or oldest) should be discarded from the queue if the queue has reached its maximum size.

Deadband Type: indicates which type of deadband to use for the monitored items:

• None

• Absolute

• Percent (for this type, the monitored item must provide EU Range engineering units)

Data Change Trigger: indicates which parameters (Status, StatusValue, StatusValueTimestamp) of the monitored item lead to notification of the client when changed.

Items per Request: specifies how many items can be read in a single request. This parameter is only used in polling mode.

Security

Use Credentials: indicates whether username and password must be used when connecting to the OPC UA server.

Username: contains username to be used in credentials.

Password: contains password to be used in credentials.

Certificate: contains security certificate for organizing a secure transmission channel. You can read about the default security certificate here.

Server Certificates

Certificate Validation Mode: Specifies server security certificate validation mode:

• Accept Any (no validation).

• Verify by Operating System (the most rigorous way of certificate validation; builds a trusted certificate chain using the operating system certificate store with validation of domain name, certificate expiration date, etc).

• Trusted Certificates List (successfully validated if the certificate is in the certificate list and is trusted).

• Trusted CA’s List (successfully validated if it is possible to build a trust chain to any of the trusted certificates on the list).

Most of the parameters described above are available as OPC UA items. More information about editing server object properties via OPC UA is described here.