I chose to check for only ':' to decide if its a IPv6 addr because it doesnt make sense to be partial towards '.' What if someone specifies a host name like 12:12;12,12 or 23:23,23,23 ? A '.' in an IPv6 addr is as bad as any other invalid char.
'.' is valid in IPv6 addr. But yes, ':' is mandatory in IPv6, and forbidden in IPv4, so it makes a good distinguishing test between the two families.
So, are you suggesting to validate IPv4 only and that too based on the absence of ':' and presence of '.'? Does that really suffice to validate an IPv4 since any other special character is also an invalid separator for IPv4 ?
Ultimately, you want to accept both types of IP addresses. I was just replying to your quote about '.' not being valid in IPv6 as being an incorrect statement; I don't really know what the best separator character is that you want to be using in this context, because I haven't been following the original conversation closely enough. You should also realize that hostnames cannot contain ':' or ';' (I'm not sure about ','), so your question about someone setting a hostname to '12:12;12,12' to confuse the parser is not worth worrying about.
Ok, I understand that IPv6 can have a '.' though ':' is mandatory in IPv6, and the current code should work for IPv6 addresses with a . as well. However, I am not sure if we need to validate the user provided hostname/IPv4/IPv6 addresses if it contains an invalid separator.
Also, the parsing code for IPv4 should work for hostnames as well. By talking about IP address with diff separators, I just meant to say that presence of . and absence of : doesnt necessarily mean a valid IPv4 address since presence of other invalid separator would also mean an invalid IPv4 address.
I didn't knew '.' is allowed in IPv6, if thats the case, then i take back my suggestion here :)