Actually, ICQ uses a direct connection between users to send messages, unless you go to the Preferences dialog and specifically tell it that it should send messages through the server. And, even then, files will still be sent directly. AFAIK, you can not store files on an ICQ server.
Since nobody else could be bothered to list them, here are a few of ICQ's features:
Here's my knowledge add for this issue:
Here is a small list that might be usefull to realize. I discovered it when setting up an IF-MS (Information Flow Management System) policy.
PS: The new releases since ICQ 2001 stores the UIN's on the Mirabilis servers ! Make sure you backup and trust Mirabilis when using this IM software.
It may seem weird that ICQ is how we communicate in my company, but before you judge, take a look at my reasoning:
I have had ICQ for several years, since close to the beginning. I know from conversations with various people that originally the numbers were assigned somewhat randomly and the fact that you had a 7-digit UIN does not necessarily render you "l33t". I originally was #5701550, but since the servers were notoriously bad at the time, they never saved any of my information so that when I finally forgot my password they refused to email it to me on the grounds that they did not have my email address on file. I was a tad miffed. Currently, that number has no info at all, although it once had my Nick of the moment.
I use ICQ to communicate with people from around the world, including people I originally met through Hardwood Hearts, Hardwood Spades, The SciFiVine (originally SciFiSites), imood, here, and various other places around the internet. I also use ICQ for the purpose of exchanging pictures, exchanging mp3s, and voice messaging. It has come a long way from the program I originally downloaded so long ago and the latest release sports a revamped User's Details window and a few fixes.
One thing particularly notable in the latest version is that the plugin options have been separated from the main program. Now, when you download ICQ, you get only the basic program. If you wish to have ICQ Voice Message, ICQ Help, or ICQ Web Front, to name a few, you will have to visit the ICQ Plug-in Center at the Mirabilis site to download those. The ICQ download is currently 5.1mb.
Unfortunately, there are some odd compatibility issues when converting the user database from ICQ99 to ICQ2000 and if you are particularly unfortunate, you may lose your entire db. This happens rarely, but when upgrading you should always backup your db in case of this so that you don't have to lose everything, although what you would do with it outside of ICQ I couldn't tell you. My db had been corrupted and I was completely unable to convert it. The loss actually freed about 148mb of space on my hard drive that had been taken up with the message history of several years.
My current UIN is 22746352, and at this moment my Nick is Neko no Aijo.
As great and useful (and secure as a wet paper bag) as the technology is, there are some minor problems with the client software.
Clearly, Mirabilis's developers (or chimps, as I like to call them) are the biggest collection of Visual Basic-reared jackasses ever to draw breath. Their client software is crammed with useless features*, and has an incredibly ugly and unintuitive interface.
An interface that, for example, doesn't use the right-click for anything apart from a message telling you to use the other button. That prints user details in grey on a grey background (and doesn't let you highlight them, or change the colours). That resizes and repositions itself stupidly whenever an OpenGL or Direct3D application does a resolution switch. That features banner ads in places where other clients don't have places. And features a barrage of crappy sounds that have to be turned off or erased to maintain your sanity.
And don't get me started on the options dialog ("look how many controls we can fit on a form!"). Why don't AOL sack these buffoons and let those fine fellows at Nullsoft (whose souls... err, company they also own) do their l33t interface-fu on it?
Thankfully, there are many alternatives available to the ICQ junkie, such as the slinky MICQ, or the highly competent Trillian.
*the SMS function is pretty cool though.
ICQ protocol wasn't published at first, but people reverse-engineered the protocol when the only client that was available for Linux was That Big, Slow, Ugly And Buggy Java Client®.
When reverse-engineered (first by Magnus Ihse), the v2 protocol turned out to be quite horrible. Apparently, the latter versions of protocol, as well, sucked similiarly but differently.
For long time, the passwords were sent unencrypted. The connections were almost always over UDP, making it (without any precautions in place against it) spoofable, hijackable, and not guaranteed to be reliable - and also difficult to deal with in places with firewalls. Also, the client developers noted the official clients were crashy when fed some bad packets...
The clients had "hooey permission bits" - you can set the permission bits all right, but the client is not required to honor them. One of these permission bits is "require authorization in order to add me to your contact list". Well, I edited my mICQ contact list and the "unaddable" users got to my contact list all right... and the users didn't even get a confirmation message that I had added them! Same thing with Everybuddy, I'm not sure if Jabber also did that...
The newer ICQ protocols have fixed the UDP problems effectively by getting rid of it and using a new, hopefully better protocol.
And since the aquisition by AOL, the new winds blow: Newest versions have apparently switched to use AIM OSCAR protocol. (thanks, fuzzie.)
(Oh: My UIN is 4291042 - I hadn't even read Douglas Adams' books yet when I first used ICQ... Though, these days I use only Jabber: wwwwolf@jabber.com.)
The latest version of ICQ - 2001b (released November 4th 2001) contains a feature which enables users to share directories on their hard-drives with users on their contact list.
This feature is quite similar to the sharing capabilities of peer to peer networks and applications such as Napster, Gnutella, KaZaA, Audiogalaxy, etc.
The only difference between these networks and the ICQ implementation is the abilty to search for the files you wish to download. It is likely that future versions of ICQ will contain this feature, and will make ICQ join the mp3 and divX piracy world, also making Mirabilis a target to legal attacks from the RIAA and similarly oriented organizations.
But even before such a search service is implemented, the broad use of ICQ may make the directory sharing feature a replacement for current 'illegal' file distribution methods such as IRC xdcc bots and fserves, FTP sites, etc.
