A better option is to use a service discovery protocol. The most popular protocol is known under the name mDNS, Avahi, Bonjour or Zeroconf. This protocol let you advertise the MQTT service on the local network and have your IoT devices find it without using an IP name or number.
Say that you run the MQTT broker Mosquitto at port 1883 on a Raspberry Pi.
Use nano to create a service description file:
sudo nano /etc/avahi/services/mosquitto.service
and paste the following text:
<!DOCTYPE service-group SYSTEM "avahi-service.dtd">
<service-group>
<name replace-wildcards="yes">Mosquitto MQTT server on %h</name>
<service>
<type>_mqtt._tcp</type>
<port>1883</port>
<txt-record>info=Publish, Publish! Read all about it! mqtt.org</txt-record>
</service>
</service-group>
Save and exit with Ctrl-O <ENTER> Ctrl-X.
Now the Avahi daemon immediately advertises the mqtt service on your local network.
To see that it works, just open any service browser - I used Bonjour Browser from http://www.tildesoft.com/ on my Mac.
Now the Avahi daemon immediately advertises the mqtt service on your local network.
To see that it works, just open any service browser - I used Bonjour Browser from http://www.tildesoft.com/ on my Mac.
On the ESP8266 side, the following code example shows how to find the MQTT server ip and port.
#include <ESP8266mDNS.h>
...
if (!MDNS.begin("ESP")) {
} else {
Serial.println("mDNS setup finished");
Serial.println("Sending mDNS Query");
int n = MDNS.queryService("mqtt", "tcp");
if (n == 0) {
Serial.println("No service found");
} else {
// at least one MQTT service is found
Serial.println("Sending mDNS Query");
int n = MDNS.queryService("mqtt", "tcp");
if (n == 0) {
Serial.println("No service found");
} else {
// at least one MQTT service is found
// ip no and port of the first one is MDNS.IP(0) and MDNS.port(0)
}
}
