|Original author(s)||Michael Sandrof|
|Developer(s)||Matthew R. Green, ircII project|
20210314 / 14 March 2021
ircII (pronounced i-r-c-two or irk-two, and sometimes referred to as IRC client, second edition) is a free, open-source Unix IRC and ICB client written in C. Initially released in the late 1980s, it is the oldest IRC client still maintained.
Several other UNIX IRC clients, including BitchX, EPIC, and ScrollZ, were originally forks of ircII. It was the first client to implement file transfer capabilities over IRC. The CTCP protocol was implemented by Michael Sandrof in 1990 for version 2.1. The DCC protocol was implemented by Troy Rollo in 1991 for version 2.1.2, and was never intended to be portable to other IRC clients.
ircII is written in the C programming language and implements a termcap, text-mode, user interface. Encrypted Transport Layer Security connections to IRC servers are established with the OpenSSL library.  The concept of file transfers over IRC networks was first implemented by the authors of ircII. The client was the first to implement both the Client-to-client protocol (CTCP) and the Direct Client-to-Client (DCC) protocol. The application has been promoted as being "fast, stable, lightweight, portable, and easily backgrounded." 
- Comparison of Internet Relay Chat clients
- Internet Citizen's Band (ICB)
- List of Internet Relay Chat commands
- History of IRCdaniel.haxx.se
- "IRC clients primarily for the Unix shell". irchelp.org. May 9, 2004. Retrieved November 10, 2010.
Note on the pronunciation of ircII: Some of us like to call it "eye-are-see-two". However, the other main variant, "irk-two" is probably historically more accurate. It's also commonly called "urk-ee" which is most definitely wrong. Feel free to disagree with us, we're not going to argue the point to death. What's pretty certain is that it is "two" and not "ee".
- Levine, John R.; Young, Margaret Levine (May 9, 1997). More Internet for Dummies (3rd ed.). Hungry Minds. p. 150. ISBN 0-7645-0135-6.
- Hahn, Harley (January 1996). The Internet Complete Reference (2nd ed.). McGraw-Hill Osborne. p. 525. ISBN 0-07-882138-X.
The irc program is sometimes called ircII (IRC client, second edition) [...]
- Schenk, Thomas (July 7, 2000). Red Hat Linux System Administration Unleashed. Sams. ISBN 0-672-31755-9.
It is probably the oldest and most commonly used IRC client in the Linux/UNIX community.
- Piccard, Paul; Brian Baskin; George Spillman; Marcus Sachs (May 1, 2005). "Common IRC Clients by OS". Securing IM and P2P Applications for the Enterprise (1st ed.). Syngress. p. 428. ISBN 1-59749-017-2.
The ircII client is possibly the oldest usable client available today.
- Piccard, Paul; Brian Baskin; George Spillman; Marcus Sachs (May 1, 2005). "IRC Networks and Security". Securing IM and P2P Applications for the Enterprise (1st ed.). Syngress. p. 386. ISBN 1-59749-017-2.
The authors of the ircII software package originally pioneered file transfers over IRC.
- See the 'NOTES' and 'source/ctcp.c' files included with ircii-2.1.4e.tar.gz[permanent dead link]
- See the 'UPDATES' and 'source/dcc.c' files included with ircii-2.1.4e.tar.gz[permanent dead link]
- Troy Rollo (January 20, 1993). "/dcc". Newsgroup: alt.irc. Usenet: 1993Jan20.email@example.com.OZ.AU. Retrieved November 10, 2010.
- Rollo, Troy. "A description of the DCC protocol". irchelp.org. Retrieved November 10, 2010.
The first comment I should make is that the DCC protocol was never designed to be portable to clients other than IRCII. As such I take no responsibility for it being difficult to implement for other clients.
- "ssl.c". 2021-03-14. Retrieved 2021-06-24.
- "IRC clients primarily for the Unix shell". IRC Help. Retrieved 2008-02-29.