Lightweight UDP / MQTT Gateway for the IoT

README.md

https://tinyurl.com/y7kmg7gv

Attempt at a quick & dirty UDP / MQTT Gateway for the IoT

Warning: The gateway is not symetric ! Read below:

UDP -> MQTT

Your UDP message must be JSON formatted in this way:

{
 "t":"<MQTT topic you want to publish to>"
 "p": <your JSON escaped payload>
}

The gateway will relay your payload to the specified topic in a transparent fashion. Messages details (source port, ip) are not provided here to avoid tampering with the payload.

As MQTT protocol doesnt have a request/response conception, we also provide a way to reply to a message by wraping the source port and message payload and relaying to to topic "/IP/udp2mqtt".

MQTT -> UDP

To relay MQTT messages to UDP, you must explicitly send your MQTT message to topic "/IP/mqtt2udp". Your MQTT message must be JSON formatted in this way :

{
 "payload":"<MQTT topic you want to publish to>"
 "dst_port": <UDP destination port>
}

If you specify src_port instead of dst_port, it will use src_port+1 as a destination port.

Using two distinct ports allows using broadcasts for both thing->server and server->thing and still be able to differentiate both traffic type.

flow.json

[
    {
        "id": "6106221f.a1af3c",
        "type": "subflow",
        "name": "full message",
        "info": "",
        "in": [
            {
                "x": 50,
                "y": 30,
                "wires": [
                    {
                        "id": "6fb46d08.bbd54c"
                    }
                ]
            }
        ],
        "out": [
            {
                "x": 620,
                "y": 60,
                "wires": [
                    {
                        "id": "6fb46d08.bbd54c",
                        "port": 0
                    }
                ]
            }
        ]
    },
    {
        "id": "6fb46d08.bbd54c",
        "type": "function",
        "z": "6106221f.a1af3c",
        "name": "",
        "func": "msg.payload = msg;\nreturn msg;",
        "outputs": 1,
        "noerr": 0,
        "x": 360,
        "y": 60,
        "wires": [
            []
        ]
    },
    {
        "id": "f299263f.262e5",
        "type": "udp in",
        "z": "524b9ce9.6e5f24",
        "name": "UDP2MQTT <gw listening UDP port>",
        "iface": "",
        "port": "<gw listening UDP port>",
        "ipv": "udp4",
        "multicast": "false",
        "group": "",
        "datatype": "utf8",
        "x": 190,
        "y": 340,
        "wires": [
            [
                "6cb01ecd.f94bd8",
                "99f420ff.f3ffd8"
            ]
        ]
    },
    {
        "id": "fd0bdea2.37a1d8",
        "type": "mqtt out",
        "z": "524b9ce9.6e5f24",
        "name": "auto topic",
        "topic": "",
        "qos": "",
        "retain": "",
        "broker": "77ea1e7c.1bf498",
        "x": 880,
        "y": 340,
        "wires": []
    },
    {
        "id": "c52f0e1a.983a98",
        "type": "function",
        "z": "524b9ce9.6e5f24",
        "name": "transparent relay to mqtt",
        "func": "msg.topic = msg.payload.t;\nmsg.payload =  msg.payload.p;\n\nreturn msg;",
        "outputs": 1,
        "noerr": 0,
        "x": 650,
        "y": 340,
        "wires": [
            [
                "fd0bdea2.37a1d8"
            ]
        ]
    },
    {
        "id": "6cb01ecd.f94bd8",
        "type": "json",
        "z": "524b9ce9.6e5f24",
        "name": "",
        "property": "payload",
        "action": "",
        "pretty": false,
        "x": 410,
        "y": 340,
        "wires": [
            [
                "c52f0e1a.983a98",
                "b8cf3aaa.c6b248"
            ]
        ]
    },
    {
        "id": "b8cf3aaa.c6b248",
        "type": "function",
        "z": "524b9ce9.6e5f24",
        "name": "wrapping relay to mqtt",
        "func": "msg.topic = \"/\" + msg.ip + \"/udp2mqtt\";\n\nmsg.payload.src_ip = undefined; //avoid duplicates\nmsg.payload.src_port = msg.port;\nmsg.payload.topic = msg.t;\nmsg.payload.payload = msg.payload.p;\nmsg.payload.t = undefined;\nmsg.payload.p = undefined;\n\nreturn msg;",
        "outputs": 1,
        "noerr": 0,
        "x": 640,
        "y": 400,
        "wires": [
            [
                "f73cc324.7edf98"
            ]
        ]
    },
    {
        "id": "f73cc324.7edf98",
        "type": "mqtt out",
        "z": "524b9ce9.6e5f24",
        "name": "/IP/udp2mqtt",
        "topic": "",
        "qos": "",
        "retain": "",
        "broker": "77ea1e7c.1bf498",
        "x": 890,
        "y": 400,
        "wires": []
    },
    {
        "id": "9d5643e.ed5534",
        "type": "json",
        "z": "524b9ce9.6e5f24",
        "name": "",
        "property": "payload",
        "action": "",
        "pretty": false,
        "x": 410,
        "y": 580,
        "wires": [
            [
                "f33ace54.53c4e"
            ]
        ]
    },
    {
        "id": "5684dda1.e8af94",
        "type": "comment",
        "z": "524b9ce9.6e5f24",
        "name": "Relay UDP to MQTT",
        "info": "",
        "x": 170,
        "y": 280,
        "wires": []
    },
    {
        "id": "edb295f3.19fba",
        "type": "comment",
        "z": "524b9ce9.6e5f24",
        "name": "Relay MQTT to UDP",
        "info": "",
        "x": 170,
        "y": 520,
        "wires": []
    },
    {
        "id": "2d65456a.c1d012",
        "type": "mqtt in",
        "z": "524b9ce9.6e5f24",
        "name": "/IP/mqtt2udp",
        "topic": "/IP/mqtt2udp",
        "qos": "2",
        "broker": "77ea1e7c.1bf498",
        "x": 170,
        "y": 580,
        "wires": [
            [
                "9d5643e.ed5534",
                "ead56341.6a88d8"
            ]
        ]
    },
    {
        "id": "f33ace54.53c4e",
        "type": "function",
        "z": "524b9ce9.6e5f24",
        "name": "relay to udp",
        "func": "msg.ip = msg.topic.split(\"/\")[1];\nmsg.port = dst_port || src_port+1;\nmsg.payload =  msg.payload.payload;\n\nreturn msg;",
        "outputs": 1,
        "noerr": 0,
        "x": 610,
        "y": 580,
        "wires": [
            [
                "179940a3.ff70df"
            ]
        ]
    },
    {
        "id": "ead56341.6a88d8",
        "type": "debug",
        "z": "524b9ce9.6e5f24",
        "name": "",
        "active": false,
        "tosidebar": true,
        "console": false,
        "tostatus": false,
        "complete": "payload",
        "x": 430,
        "y": 520,
        "wires": []
    },
    {
        "id": "179940a3.ff70df",
        "type": "udp out",
        "z": "524b9ce9.6e5f24",
        "name": "UDP auto port/ip",
        "addr": "",
        "iface": "",
        "port": "",
        "ipv": "udp4",
        "outport": "",
        "base64": false,
        "multicast": "false",
        "x": 910,
        "y": 580,
        "wires": []
    },
    {
        "id": "69affc7.2fcc284",
        "type": "debug",
        "z": "524b9ce9.6e5f24",
        "name": "",
        "active": true,
        "tosidebar": true,
        "console": false,
        "tostatus": false,
        "complete": "false",
        "x": 630,
        "y": 200,
        "wires": []
    },
    {
        "id": "99f420ff.f3ffd8",
        "type": "subflow:6106221f.a1af3c",
        "z": "524b9ce9.6e5f24",
        "x": 380,
        "y": 220,
        "wires": [
            [
                "69affc7.2fcc284"
            ]
        ]
    },
    {
        "id": "77ea1e7c.1bf498",
        "type": "mqtt-broker",
        "z": "",
        "name": "<IP of your MQTT broker>",
        "broker": "<IP of your MQTT broker>",
        "port": "1883",
        "clientid": "",
        "usetls": false,
        "compatmode": true,
        "keepalive": "60",
        "cleansession": true,
        "willTopic": "",
        "willQos": "0",
        "willPayload": "",
        "birthTopic": "",
        "birthQos": "0",
        "birthPayload": ""
    }
]

Please take a look at https://github.com/dzavalishin/mqtt_udp - a complete UDP based implementation of MQTT-based protocol