3.3. Service Discovery

The ESP Thread Border Router allows devices on the Thread and Wi-Fi/Ethernet network to discover services published on both the networks.

Hardware Prerequisites

To perform service discovery, the following devices are required:

An ESP Thread Border Router
A Thread CLI device
A Linux Host machine

The Border Router and the Linux Host machine shall be connected to the same Wi-Fi network and the Thread device shall join the Thread network formed by the Border Router.

Publishing Services from the Thread Network

Thread uses the Service Registration Protocol (SRP) to register services. First, publish the service on the Thread CLI device.

Using this command line to set host name:

srp client host name thread-device

Using this command line to set host address, you can set default address with auto:

srp client host address auto

Using this command line to set parameter of the service:

srp client service add thread-service _test._tcp,_sub1,_sub2 12345 1 1 0778797a3d58595a

Using this command line to enable the service:

srp client autostart enable

You will get a result Done after executing each of the commands, the expected output is below:

> srp client host name thread-device
Done
> srp client host address auto
Done
> srp client service add thread-service _test._tcp,_sub1,_sub2 12345 1 1 0778797a3d58595a
Done
> srp client autostart enable
Done

You can execute this command on the Border Router to resolve the service:

srp server service

The service can be found on the Border Router:

> srp server service
thread-service._test._tcp.default.service.arpa.
    deleted: false
    subtypes: _sub2,_sub1
    port: 12345
    priority: 1
    weight: 1
    ttl: 7200
    TXT: [xyz=58595a]
    host: thread-device.default.service.arpa.
    addresses: [fd66:afad:575f:1:744d:573e:6e60:188a]
Done

The service can also be found on the Wi-Fi with the Linux Host machine by using this command:

avahi-browse -rt _test._tcp

The expected output is below:

$ avahi-browse -rt _test._tcp
+ enp1s0 IPv6 thread-service                                _test._tcp           local
+ enp1s0 IPv4 thread-service                                _test._tcp           local
= enp1s0 IPv6 thread-service                                _test._tcp           local
   hostname = [thread-device.local]
   address = [fd66:afad:575f:1:744d:573e:6e60:188a]
   port = [12345]
   txt = ["xyz=XYZ"]
= enp1s0 IPv4 thread-service                                _test._tcp           local
   hostname = [thread-device.local]
   address = [fd66:afad:575f:1:744d:573e:6e60:188a]
   port = [12345]
   txt = ["xyz=XYZ"]

Publishing Services from the Wi-Fi Network

First publish the service on the Linux Host machine with mDNS:

avahi-publish-service wifi-service _test._tcp 22222 test=1 dn="aabbbb"

If the service is established, you will get this output on your Linux Host machine:

$ avahi-publish-service wifi-service _test._tcp 22222 test=1 dn="aabbbb"
Established under name 'wifi-service'

Then get the Border Router’s Mesh-Local Endpoint Identifier, and configure it on the Thread end device. On the Border Router:

ipaddr mleid

You will get:

> ipaddr mleid
fdde:ad00:beef:0:f891:287:866:776
Done

On the Thread CLI device:

dns config fdde:ad00:beef:0:f891:287:866:776

You will get:

> dns config fd9b:347f:93f7:1:1003:8f00:bcc1:3038
Done

The service can be resolved on the Thread CLI device by executing this command:

dns service wifi-service _test._tcp.default.service.arpa.

The expected output on the Thread CLI device is below:

> dns config fdde:ad00:beef:0:f891:287:866:776
Done
> dns service wifi-service _test._tcp.default.service.arpa.
DNS service resolution response for wifi-service for service _test._tcp.default.service.arpa.
Port:22222, Priority:0, Weight:0, TTL:120
Host:FA001388.default.service.arpa.
HostAddress:fd33:1cc4:a6ec:2e0:2eea:7fff:fe37:b4fb TTL:120
TXT:[test=31, dn=616162626262] TTL:120

Done