DNS
The DNS feature resolves hostnames such as api.example.com into IP addresses. Any feature that connects to a server by name depends on it, including the HTTP Client, MQTT and the SMTP Client.
DNS is added to the project automatically when a feature that needs it is enabled. You only need to open it to change the name servers or the timeout.
Configuration
- DNS Enabled: turns the resolver on. The other properties are hidden while it is off.
- Server 1: primary DNS server. Defaults to
8.8.8.8(Google Public DNS). - Server 2: optional secondary DNS server, used if the primary does not answer.
- DNS Reply Timeout(ms): how long to wait for a DNS reply before the lookup fails. Defaults to
5000.
tip
On a private network without internet access, point Server 1 at your local DNS server, often your router's address, so local hostnames resolve.
Troubleshooting
If requests to a hostname fail but requests to the same server by IP address succeed:
- Check that the device has a working network connection and gateway.
- Confirm the DNS server is reachable from the device's network. Some networks block outside DNS servers such as
8.8.8.8. - Increase DNS Reply Timeout on slow or cellular links.