Multicast DNS Service

Multicast DNS (mDNS) is a protocol that sends one to many network packages containing DNS information records. This is also known as zeroconf or bonjour protocol and allows finding network devices without the need for a dedicated central DNS server.

The advantage of mDNS in in announcing not just IP addresses but also the kind of service offered by a device.

There is a bunch of services in the IoT space that already uses this protocol and it can be seen as a quasi standard:

can be disabled by setting the sd (Service Discovery) property in the configuration of the Device Element to false.

CLI tool to discover HomeDing devices

The WebFiles project https://github.com/HomeDing/WebFiles that implements a central portal to show all devices offers a command line tool to list existing devices by using the command: node discoverDevices.js.

mDNS implementation

In the devices the mDNS implementation is covered by the ESP8266mDNS/ESPmDNS library provided by the Arduino board base firmware.

In the portal and the CLI tool the mDNS implementation is covered by the multicast-dns javascript library.

http:////api/discovery

{
  "airding":{
    "host":"airding.local",
    "title":"",
    "path":"/board.htm",
    "ts":"2021-05-09T11:28:56.486Z"
  },
  "rfbridge":{
    "host":"rfbridge.local",
    "title":"Funk Schaltsteckdosen",
    "path":"/board.htm",
    "ts":"2021-05-09T11:28:56.485Z"
  }
}

Used in the Home Portal solution. multicast DNSservice

See also

• DNS-Based Service Discovery https://datatracker.ietf.org/doc/html/rfc6763
• Simple Service Discovery Protocol (SSDP) Element
• Device Element

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