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The OPC UA protocol is the next generation of the OPC standard, which provides a cohesive, secure, and reliable platform-independent framework for access to the real time data. The main difference in comparison with the previous versions is that the interprocess communication uses TCP/IP communication instead of COM/DCOM technology and therefore is OS (Windows) independent. This protocol supports two methods of data encoding (binary and XML). The existing OPC client implementation supports only binary encoding.
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When initiating the communication, the client exchanges multiple messages with the server. In the case of binary encoding, "Hello Message" isthe first message sent from the client to the server. The message defines the size of receiving and sending buffers and the maximum size of messages that may be exchanged during TCP communication between client and server. It also defines the URL address of the endpoint. The server answers by sending sending an "Acknowledge message", in which it confirms the suggested parameters or modifies them according to its limits.
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| Parameter name | Meaning | Unit | Default value | ||||||
|---|---|---|---|---|---|---|---|---|---|
| Type of used client (driver for OPC UA communication):
| Default Secure | Default | ||||||
| Session text identifier. Session identifier should be a unique within the client instance, making it possible to search problems faster in the client or server logs. | String | Kom process | ||||||
| The channel must be reopened before this time limit elapses. If the time is exceeded, the channel will be closed and unable to change data. | hh:mm:ss | 01:00:00 | ||||||
| Any message should be changed between client and server before this time limit elapses. If it is not sent, the sources within the session that are kept on the server are released. The primary work of this parameter is to remove the sessions that became inactive because of some unexpected reason. | mm:ss | 01:00 | ||||||
| Type of authentication used with the OPC UA server. Supported types are:
| Anonymous / Username | Anonymous | ||||||
| User If Authentication type = Username, then user name used in the authentication if . If Authentication type = UsernameCertificate, then path to user certificate (e.g. D:\user_cert.der). | ||||||||
| Password If Authentication type = Username, then password used in the authentication if . If Authentication type = UsernameCertificate, then path to user private key (e.g. D:\user_private_key.pem). | ||||||||
| Security policy (only for Client Type = Secure; for Client Type = Default a security policy None is used):
| None Basic128Rsa15 Basic256 Basic256Sha256 Aes128Sha256RsaOaep Aes256Sha256RsaPss | None | ||||||
| A mode of message security in OPC UA communication (only for Client Type = Secure; for Client Type = Default a mode of message security None is used):
| None Sign Sign & Encrypt | None | ||||||
| Waiting after the connection is broken before the connection is re-established. | mm:ss.mss | 00:10.000 | ||||||
| Waiting after an unsuccessful connection attempt. | mm:ss.mss | 00:02.000 | ||||||
| It changes the number of information about communication. We recommend enabling the Extended/Full modes only when detecting the problems and debugging the communication. The "Full + Trace (Secure only)" mode is valid only for Client Type = Secure. | Normal/Extended/Full/ Full + Trace (Secure only) | Normal | ||||||
| The parameter defines the thread(s) that will send the debug info about the communication. | Receiving/Sending/Others treads/All threads | All threads |
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