The following table shows how the command is encoded for network transmission:
| Type | Name | Description |
|---|---|---|
| uint8 | id = 17 | The command byte that identifies this command. |
| VNodeID | node_id | The ID of the node being accessed. |
| uint16 | group_id | The ID of the tag group to which a client wishes to subscribe. |
| uint8 | alias = 1 | If this field is zero (FALSE), aliasing is activated, and the command should be interpreted as a tag_group_unsubscribe instead. It is encoded as one (TRUE) to indicate tag_group_subscribe. |
This command is sent by a client that wishes to subscribe to a tag group.
If the request is granted by the host, it will add the client to the list of subscribers to the referenced tag group, and send a description of its current contents. The host will continue to send updates as the contents change, until the client unsubscribes or the tag group is destroyed. If the request to subscribe is denied, nothing happens.
It is only possible to subscribe once to a specific tag group, any further attempts to subscribe will have no effect.