How to handle IDENTIFY request in Google Smart Home Local Fulfilment for multi channel device?

Question

I am trying to implement Local Fulfillment in my Google Smart Home Action. some of my devices have 2 channels (dual relay switch).
Dual channel device is shown in Google Home app as two separate devices(light-test123123_0 and light-test123123_1) and it works just fine.

I have added customData and otherDevicesIds to my SYNC response to enable local fultilment and built an local app using @google/local-home-sdk. Google Home identifies Single channel devices and sends commands locally.

example of SYNC response body:

{
    "response": {
        "payload": {
            "devices": [
                {
                    "traits": [
                        "action.devices.traits.OnOff",
                        "action.devices.traits.Brightness"
                    ],
                    "customData": {
                        "path": "/local-fulfil/0/",
                        "port": 3000
                    },
                    "name": {
                        "name": "light",
                        "nicknames": [
                            "light"
                        ],
                        "defaultNames": [
                            "light"
                        ]
                    },
                    "id": "light-test123123_0",
                    "type": "action.devices.types.LIGHT",
                    "deviceInfo": {
                        "hwVersion": "LIGHT",
                        "model": "LIGHT",
                        "swVersion": "1.0",
                        "manufacturer": "MANUFATURER"
                    },
                    "attributes": {},
                    "willReportState": false,
                    "otherDeviceIds": [
                        {
                            "deviceId": "light-test123123_0"
                        },
                        {
                            "deviceId": "light-test123123"
                        }
                    ]
                },
                {
                    "name": {
                        "nicknames": [
                            "light"
                        ],
                        "defaultNames": [
                            "light"
                        ],
                        "name": "light"
                    },
                    "deviceInfo": {
                        "swVersion": "1.0",
                        "hwVersion": "LIGHT",
                        "manufacturer": "MANUFATURER",
                        "model": "LIGHT"
                    },
                    "attributes": {},
                    "otherDeviceIds": [
                        {
                            "deviceId": "light-test123123_1"
                        },
                        {
                            "deviceId": "light-test123123"
                        }
                    ],
                    "willReportState": false,
                    "traits": [
                        "action.devices.traits.OnOff",
                        "action.devices.traits.Brightness"
                    ],
                    "id": "light-test123123_1",
                    "customData": {
                        "port": 3000,
                        "path": "/local-fulfil/1/"
                    },
                    "type": "action.devices.types.LIGHT"
                }
            ],
            "agentUserId": "RuRHIPWpD5W23iGiU81A5PoTKqB2"
        },
        "requestId": "16772679358918515269"
    }
}

The problems appeared when I have started the local SDK implementation because even if my dual channel device sends 2 separate UDP packets with different IDs mentioned above. Google ignores one of them. Looks like it is not possible to have 2 devices with same IP address.

Here is the IDENTIFY request body:

{
    "requestId": "88DB84992F074FF0B408D8383CF198C4",
    "inputs": [
        {
            "intent": "action.devices.IDENTIFY",
            "payload": {
                "device": {
                    "udpScanData": {
                        "data": "6C696768742D6475616C2D3132335F30"
                    }
                },
                "structureData": {}
            }
        }
    ],
    "devices": [
        {
            "id": "light-dual-123_0",
            "customData": {
                "path": "/local-fulfil/0/",
                "port": 3000
            }
        },
        {
            "id": "light-dual-123_1",
            "customData": {
                "path": "/local-fulfil/1/",
                "port": 3000
            }
        }
    ]
}

and response:

{
    "intent": "action.devices.IDENTIFY",
    "requestId": "88DB84992F074FF0B408D8383CF198C4",
    "payload": {
        "device": {
            "id": "",
            "verificationId": "light-test123123_0"
        }
    }
}

I have written a basic app that sends UDP broadcast and it outputs the next data:

sent broadcast packet
192.168.1.235:8888 sent this: light-test123123_0
192.168.1.235:8888 sent this: light-test123123_1

That shows how my device acts when it receives a broadcast packet.

Is there a way to fix this?

Answer 1

The Local Fulfillment platform currently (as of Local Home SDK 1.4) uniquely identify the device by their network address, so it won't be able to handle multiple broadcast response coming from the same physical connected device.

You can however have one device acting as a proxy for multiple end-devices, this is done by:

• returning setting the isProxy flag to true in the IDENTIFY response: https://developers.google.com/assistant/smarthome/develop/local#hub-identify
• handling the REACHABLE_DEVICES intent to return all the end-device verificationId: https://developers.google.com/assistant/smarthome/develop/local#hub-identify

The Local Home SDK sample includes a virtual device that can be run in this configuration: https://github.com/actions-on-google/smart-home-local#set-up-the-virtual-device