Full DNS vs IP number

[EA5SW]

We have observed the following: If the address of the master is a full domain name and for example, the system like a Raspberry pi does not have access to the internet, the program stops running.

However, if we change the address of the master for an IP number when the Raspberry Pi manages to connect to the internet and have a valid IP, the program is able to reconnect to the master.

Is it possible that this explains the problems that some users comment on not being able to reconnect after a network failure ???

[jg1uaa]

Accessing DNS server is blocked (and error at CUDPSocket::lookup()) or already got IP address, that is difference.

Well, this is same thing; how does network interface that is marked "down" obtain IP address from DHCP server? I think there is no treatment.

[jg1uaa]

Original design uses IP address, no FQDN. Should I add AI_NUMERICHOST to hints.ai_flags, to disable FQDN?