isIPv4 static method
Returns true if the host is an IPv4 address.
Implementation
static bool isIPv4(String host) {
final parts = host.split('.');
if (parts.length != 4) return false;
for (final part in parts) {
final value = int.tryParse(part);
if (value == null || value < 0 || value > 255) return false;
}
return true;
}