Data Items

A data item on a DataSocket Server represents a real-world measurement. DataSocket Readers can subscribe to data items on a DataSocket Server, and DataSocket Writers can create and publish or update data items on a DataSocket Server.

There are two types of data items—predefined data items and dynamically created data items:

• Predefined data items always exist on the DataSocket Server, and they always have an initial value associated with them. Because the DataSocket Server never releases predefined data items, their values exist even when no DataSocket client is connected to them. Predefined data items can have special read and write access groups so you can allow different computers to access different predefined data items.
• Dynamically created data items exist only as long as there is at least one DataSocket client connected to read or write the data item value. When no connections to a dynamically created data item remain, the DataSocket Server releases the data item and its value.

By default, only programs running on the same computer as the DataSocket Server can create data items or publish to data items, whereas applications on the same computer or other computers can read data items. Use the DataSocket Server Manager to specify which computers can create data items, publish to data items, and subscribe to data items.