The library OPC UA PubSub SL allows for the exchange of messages via the Pub/Sub protocol defined by the OPC UA Foundation.
Communication via the OPC UA Pub/Sub protocol provides, in addition to the Client/Server communication, also a possibility to exchange data between the subscribers of a network in compliance with the rules of the OPC UA Foundation. The structure of the data (DataSet) can be freely defined and is agreed in advance between the sender and the receiver. This eliminates the need to transport additional (meta)data. The data transfer takes place with the help of the OPC UA PubSub SL library via UDP/IP according to the rules defined for UADP. A Publisher publishes its data to an unknown number of Subscribers. So the sender and receiver do not know each other. That is why the number of receivers also does not have any repercussions for the sender. A reply to the sender as to whether its messages have reached the receivers cannot be sent via the protocol due to the nature of the protocol. If necessary, such a reply has to be managed in an application-specific way. The data is transferred in a binary format according to the rules of the OPC UA Foundation. The OPC UA PubSub SL library takes over the conversion of IEC data types into the corresponding OPC UA data types and back. The implementation thereby follows the profiles below:
Publisher: PubSub Publisher UADP Periodic Fixed Settings
Subscriber: PubSub Subscriber UADP Periodic Fixed Settings
The message length is limited to 1500 bytes (MTU) (Chunked NetworkMessages not supported). As long as the rules for a Time Sensitive Network is still not available, hard real-time conditions cannot be complied with. However, the implementation of the OPC UA PubSub SL library attempts to keep the jitter as low as possible.
Development system | CODESYS Development System V3.5.17.0 or higher |
Runtime | CODESYS Control V3.5.14.0 or higher |
Supported platforms and devices | Note: Use the “Device Reader” project for locating the functions supported by the PLC. The Device Reader is available in the CODESYS Store free of charge. |
Additional requirements | Depending on the capabilities of the respective runtime system, the messages can be sent via Unicast, Multicast, or Broadcast. |
Restrictions | The maximum length of a Networkmessage is 1500 bytes. (Chunked NetworkMessages not supported) |
Licensing |  Single device license: The license can be used on the target device/PLC on which the CODESYS runtime system is installed. Licenses are activated on a software-based license container (soft container), which is permanently connected to the controller. Alternatively, the license can be stored on a CODESYS Key (USB dongle). By replugging the CODESYS Key, the license can be used on any other controller. Note: Without a license, the software runs for 30 minutes demo mode. A manual restart is required after that. |
Required accessories | - |
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For general error messages or pre-sales inquiries, please use the "My Question" contact form directly, which can also be used without logging in. A list of alternative support resources can be found in the support section of the CODESYS Group website.
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