- OSCAR protocol
OSCAR or Open System for CommunicAtion in Realtime is AOL's flagship instant messaging and presence information protocol. Currently, OSCAR is in use for AOL's two main instant messaging systems: ICQ and AIM.
Despite its name, the specifications for the protocol remain proprietary. AOL has gone to great lengths to keep competitors (namely Microsoft, XMPP, and Cerulean Studios) from implementing compatible clients for their proprietary messaging systems. In 2002, AOL signed a contract with Apple, Inc., allowing them to use OSCAR (as well as AOL's own code libraries) in their iChat application. This allowed iChat users to interact with ICQ and AIM users directly. The deal also permitted users of Apple's .Mac service to log into the AIM network using their .Mac email addresses. (This has carried over to Apple's MobileMe service.)
The OSCAR protocol can be used separately from AOL's network. In fact, AOL expands on the general concept of OSCAR, adding systems for service side buddy lists and icons, as well as features for file transfers (using Bonjour.)
On March 6, 2006, AOL released the AIM SDK and launched a developer website, allowing developers to build plugins for AIM Triton, and build their own custom clients, which connect over the OSCAR protocol. They had not, at that point, however, released any information about the protocol itself.
On March 5, 2008, AOL released portions of the OSCAR protocol documentation. Google also provides the ability to sign into AIM network via the Google Talk client built into Gmail.
All packets sent over OSCAR are encapsulated in the same manner. All 16-bit integers sent over the network are unsigned, and big endian (see Endianness.) This is the same for 32-bit integers, and 8-bit integers (or bytes.)
A special FLAP (Frame Layer Protocol) container encloses every packet. It carries information about packet size, channel, and its number in sequence.
Offset (hex) Field Type/Size (in bytes) Remarks 00 FLAP ID byte/1 Always contains 2A. It is mark of packet start. 01 Channel byte/1 1 = login, 2 = SNAC layer, 3 = error, 4 = disconnect 02 Number in sequence int16/2 Incremented by 1 each time a packet sent. Wraps to 0 after FFFF. 04 Data size int16/2 Size does not include FLAP header
Within almost every packet sent over channel 2, packets contain a SNAC (Simple Network Atomic Communication). There is always either one or zero of these contained in a packet, and therefore they do not contain (nor do they need to) a length.
Offset (hex) Field Type/Size (in bytes) Remarks 00 Foodgroup int16/2 The general type of the packet 02 Type int16/2 The specific type of the foodgroup 04 Flags int16/2 06 Request ID int32/2 A request ID, this can be random but clients cannot send this with the Highest Order Bit set.
- Comparison of instant messaging clients
- Comparison of instant messaging protocols
- TOC protocol, AOL's free but deprecated messaging protocol
- TOC2 protocol, as of 2009[update], the current version of the TOC protocol
- Official OSCAR-Documentation (Requires Login) - No longer available (12.07.2010)
- UnOfficial AIM/OSCAR Protocol Specification
- Archived Official Documentation
- FAIM: FAIM/AIM/OSCAR Protocol Specification
Implementations C libpurple
C# NOscar C++ QOscar (Qt) C# 2.0 OscarLib Java joscar
Instant Messenger Lib
OCaml mlOscar Python TwistedWords Perl Net::OSCAR PHP WebIcqPro
Instant messaging Protocols
See alsoClients by protocol (comparison) Single protocol Multi-protocol XMPP (Jabber) .NET Messenger This article related to telecommunications is a stub. You can help Wikipedia by expanding it.