Regular expression to match DNS hostname or IP Address?

Question

Does anyone have a regular expression handy that will match any legal DNS hostname or IP address?

It\'s easy to write one that works 95% of the time, but I\'m hoping

Answer 1

The new Network framework has failable initializers for struct IPv4Address and struct IPv6Address which handle the IP address portion very easily. Doing this in IPv6 with a regex is tough with all the shortening rules.

Unfortunately I don't have an elegant answer for hostname.

Note that Network framework is recent, so it may force you to compile for recent OS versions.

import Network
let tests = ["192.168.4.4","fkjhwojfw","192.168.4.4.4","2620:3","2620::33"]

for test in tests {
    if let _ = IPv4Address(test) {
        debugPrint("\(test) is valid ipv4 address")
    } else if let _ = IPv6Address(test) {
        debugPrint("\(test) is valid ipv6 address")
    } else {
        debugPrint("\(test) is not a valid IP address")
    }
}

output:
"192.168.4.4 is valid ipv4 address"
"fkjhwojfw is not a valid IP address"
"192.168.4.4.4 is not a valid IP address"
"2620:3 is not a valid IP address"
"2620::33 is valid ipv6 address"