Regex: IP address - how to check it

When you want to check a string for certain properties in computer science, regular expressions are usually used. With regex, it is thus possible to describe a set of strings. For example, you can validate the input of an IP address.

This is how to validate an IP address with Regex

For some programs it is necessary to enter an IP address in order to connect to a server, for example. In this case, it is necessary to validate the input to prevent it from being incorrect. If you want to check whether a string represents a valid IPv4 address, you have several options.

1. For example, if you use the regex "^(?:[0-9]{1,3}\.){3}[0-9]{1,3}$", then you check the form of the input, but in doing so 999.999.999.999 as validated - although it is obviously not a valid iPv4 IP address.
2. In order to additionally check whether the individual number blocks are between 0 and 255, you must write the following " ^(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$“.
3. When representing an iPv6 address, however, this can become much more complex, as there are also numerous ways to represent an IP address shorter here, for example, expressions that exist only as 0 are replaced with "::".
4. Vor allem bei der Überprüfung einer IPv6-Adresse bietet es sich daher an, spezielle Tools zum Testen Ihres Regex zu nutzen. Im Internet finden Sie dazu zahlreiche Seiten, auf denen Sie Ihre regulären Ausdrücke testen können.