nodemcu-firmware/docs/modules/mdns.md

mDNS Module

Since	Origin / Contributor	Maintainer	Source
2016-02-24	Philip Gladstone	Philip Gladstone	mdns.c

Multicast DNS is used as part of Bonjour / Zeroconf. This allows systems to identify themselves and the services that they provide on a local area network. Clients are then able to discover these systems and connect to them.

!!! note

This is a mDNS *server* module. If you are looking for a mDNS *client* for NodeMCU (i.e. to query mDNS) then [udaygin/nodemcu-mdns-client](https://github.com/udaygin/nodemcu-mdns-client) may be an option.

mdns.register()

Register a hostname and start the mDNS service. If the service is already running, then it will be restarted with the new parameters.

Syntax

mdns.register(hostname [, attributes])

Parameters

• hostname The hostname for this device. Alphanumeric characters are best.
• attributes A optional table of options. The keys must all be strings.

The attributes contains two sorts of attributes — those with specific names, and those that are service specific. RFC 6763 defines how extra, service specific, attributes are encoded into the DNS. One example is that if the device supports printing, then the queue name can be specified as an additional attribute. This module supports up to 10 such attributes.

The specific names are:

• port The port number for the service. Default value is 80.
• service The name of the service. Default value is 'http'.
• description A short phrase (under 63 characters) describing the service. Default is the hostname.

Returns

nil

Errors

Various errors can be generated during argument validation. The NodeMCU must have an IP address at the time of the call, otherwise an error is thrown.

Example

mdns.register("fishtank", {hardware='NodeMCU'})

Using dns-sd on macOS, you can see fishtank.local as providing the _http._tcp service. You can also browse directly to fishtank.local. In Safari you can get all the mDNS web pages as part of your bookmarks menu.

mdns.register("fishtank", { description="Top Fishtank", service="http", port=80, location='Living Room' })

mdns.close()

Shut down the mDNS service. This is not normally needed.

Syntax

mdns.close()

Parameters

none

Returns

nil