Communication on this Jabber server is limited to Argonne employees, but you can use the service from home without VPN. Jabber is an open source, secure, ad-free alternative to consumer instant messaging (IM) services such AIM, ICQ, MSN, and Yahoo. The UIN was invented by Mirabilis, as the user name assigned to each user upon registration.

ICQ users are identified and distinguished from one another by UIN, or User Identification Numbers, distributed in sequential order. If you’re interested in reconnecting with old contacts or want to discover it for the first time, ICQ is available to download for Windows and Mac as well as Android and iOS mobile devices. Some may be surprised to learn that ICQ is still around and is being actively developed. You have to go with your browser to and login there…. ICQ does not show you your UIN by default. Now you have your ICQ account! But at the moment, you can only login with Kopete using UINs (Unified Identification Number). You can recover your account password only if an email or phone number is associated with it and you have access to them. There you can enter the UIN of the person you want to add. To add a contact press Add in the toolbar and choose your account (in this case it is your UIN), or you can use the menu File -> Add Contact -> your account.

Http search icq com