In the Device resource for FHIR r4 , the url attribute identifies the Network address to contact device
"url":
"identifier": [
{
"system": "http://goodcare.org/devices/id",
"value": "345675"
}
]
"definition":
"udiCarrier":
"status":
"statusReason":
"distinctIdentifier":
"manufacturer":
"manufactureDate":
"expirationDate":
"lotNumber":
"serialNumber":
"deviceName":
"modelNumber":
"partNumber":
"type":
"specialization":
"version":
"property":
"patient":
"owner":
"contact":
"location":
"url":
"note":
"safety":
"parent":