I have just fixed the problem with YAMS not allowing you to set IP addresses as server names in my bleeding edge version. If you would like to repair the problem in your version until I finalise the release, do the following:
1. Open yams.class.inc.php.
2. Find the declaration for the function SetMonoServerName.
3. Replace the regexp string by
'/^(|(?:[a-z0-9]\.|[a-z0-9][-a-z0-9]{0,61}[a-z0-9]\.)*(?:com|edu|gov|int|mil|net|org|biz|info|aero|[a-z][a-z]|[0-9]{1,3}))$/i'
4. Find the declaration for the function SetServerName
5. Make the same replacement within the preg_match.
You should then be able to set an IP based address as your server name.
EDIT: Updated to include points 4 and 5.