Native modern mobile client uses HTTP based protocol which supports recently added features.Īccording to Mail.Ru Group audited annual report, in December 2013 ICQ had 11 million monthly active users. Note that all publicly available information in the Internet about ICQ protocol describing legacy binary protocol called OSCAR. Our custom build system created C-functions which pack/unpack OSCAR messages Ĩ) Huge portion of core code-base was dedicated to create very scalable distributed server architecture Here are some quick facts about ICQ backend infrastructure:ġ) ICQ servers has over 2'700'000 lines of code which is written in C and C++ Ģ) ICQ has its own TCP/IP implementation which works in the user space ģ) Concurrency based on event-driven model (epoll), each instance handles many requests semi-simultaneously Ĥ) About 60 different interconnected internal services ĥ) Each kind of backend service is a cluster of more than a hundred of instances Ħ) C core-code is written in old-school style and I liked that ħ) OSCAR protocol is defined in TCL files. I was enjoyed working with ICQ backend code-base written by AOL (although to be honest not all code was high quality). I started to work at Mail.Ru in 2010, when Mail.Ru bought ICQ from AOL.

I'm former ICQ backend developer (2010 - 2014).

Icq app lock