Optimised request: client has devices list of specific version already and asks about the changed one:

Edit 
				
					{
    "id": "_ID_",
    "api": "1.0",
    "method": "hub.device.item.group.expand",
    "params": {
        "deviceGroupId": "642e5cf500000011965a8af5",
        "version": "37095e6a9af5f92895099c7ddddd3c23caface71"
    }
}
Edit 
				
					{
    "api": "1.0",
    "error": null,
    "id": "_ID_",
    "result": {
    "version": 9127155317259983000
    }
}