ICQ

From Protocolinfo

The ICQ protocol was originally developed by Mirabilis, Inc., which was later bought by AOL. Although the protocol was never open, there have been several groups which have attempted to reverse-engineer it. Most of them are cooperating now, sharing the information they've obtained about it. Gaim, for instance, is able to use ICQ thanks to icqlib.

The original version of the ICQ protocol is based on both UDP and TCP. The connection with the server is UDP, and messages such as who's online are sent via UDP. When you have a conversation with someone, you connect to them using TCP, and messages are sent directly. It is possible to send messages through the server in cases where direct TCP connections aren't possible. Direct TCP connections are also established for file transfers and chats.

ICQ99 was the last official ICQ client to use the UDP-based protocol. Starting with ICQ2000, the official ICQ client uses a modified version of Oscar.

ICQ2Go is a web based version of ICQ which communicates over HTTP.

Contents 1 Identification 1.1 Servers 1.2 Ports 1.3 l7-filter 2 See also 3 Credits

[edit] Identification

[edit] Servers

ICQ uses centralized servers in the icq.com domain to log in.

[edit] Ports

ICQ uses TCP port 5190 for Oscar communications.

[edit] l7-filter

Because ICQ uses Oscar, it can be matched using the aim pattern.

[edit] See also

• Wikipedia's ICQ article

[edit] Credits

Some text on this page is courtesy of the Gaim project.