Port 6660: IRC — Where the Conversation Begins

Port 6660 carries Internet Relay Chat (IRC) traffic. It is the first port in IRC's traditional range of 6660-6669, a corridor of doors that has carried real-time human conversation across the Internet since 1988.

When you connect to an IRC server on port 6660, you are using a protocol older than the World Wide Web itself.

How IRC Works

IRC operates on a simple client-server model. You connect your IRC client to a server, join channels (chat rooms prefixed with #), and exchange text messages in real time. Messages follow a straightforward structure: an optional prefix identifying the sender, a command, and parameters, all as plain text terminated by a carriage return and line feed.¹

The protocol's elegance lies in its simplicity. Each message cannot exceed 512 characters.¹ Servers form a spanning tree topology, routing messages efficiently across the network. Channels appear when the first user joins and vanish when the last user leaves. No persistent state, no databases required, just text flowing through connections.

One quirk reveals IRC's Scandinavian origins: the characters {}| are treated as lowercase equivalents of []\ respectively.¹ A small artifact of Finnish keyboards, baked into a protocol used worldwide.

Why Port 6660?

IANA officially assigned port 194 for IRC traffic.² So why does no one use it?

Port 194 is a privileged port. On Unix systems, binding to any port below 1024 requires root access. The early IRC community, made up of students and researchers without administrative control over their machines, chose instead to run on unprivileged ports where anyone could start a server.³

The range 6660-6669 became the convention, with 6667 as the default. These numbers have no technical significance. They were simply available, memorable, and stuck. IANA eventually registered ports 6665-6669 for IRCU (the Undernet IRC daemon), formalizing what the community had already established.⁴

Port 6660 is the opening note of this range. Not the most commonly used (that honor goes to 6667), but the beginning of a tradition.

The Origin Story

In the summer of 1988, a 20-year-old student named Jarkko Oikarinen was working at the University of Oulu in Finland. He administered a Sun-3 Unix server called tolsun.oulu.fi, which ran a BBS called OuluBox. The BBS had a multi-user chat program called MUT (MultiUser Talk), and it had a bad habit of not working properly.⁵

Oikarinen decided to fix it. Inspired by Bitnet Relay Chat and a messaging program his friend Jyrki Kuoppala had written, he created something new. He called it IRC, for Internet Relay Chat, though as he later admitted, "The name was definitely more ambitious than the original intention."⁶

The first IRC server went live in August 1988. When it started getting more than 10 users, Oikarinen asked friends at other Finnish universities to run servers to distribute the load. IRC spread across Finland's national network (FUNET), then to Scandinavia (NORDUNET), then to the world.⁵

By 1989, there were 40 servers worldwide. By 1991, IRC would carry something no chat system had ever carried before.

The Gulf War Moment

In January 1991, when coalition forces began bombing Iraq, IRC carried real-time reports from people on the ground. While CNN broadcast from Baghdad, ordinary users on IRC shared what they were seeing and hearing. The protocol designed for Finnish university students was carrying war correspondence.⁷

IRC had become infrastructure.

The Protocol

RFC 1459, published in May 1993 by Jarkko Oikarinen and Darren Reed, formally documented the IRC protocol.¹ The core concepts remain unchanged today:

Clients connect to servers with a nickname (originally limited to 9 characters) and join channels.

Channels are named groups that begin with a # character. Anyone can create one by joining it. Channel operators (ops) control who can speak, who can join, and who gets kicked.

Messages flow through the server network. Private messages go directly between users. Channel messages broadcast to everyone in the room.

Servers link together in a spanning tree. When servers disconnect (a "netsplit"), the network fragments until they reconnect. This architecture, elegant for its time, became a source of chaos as IRC grew.

The Splits

IRC's history is a history of fragmentation.

In August 1990, a server called eris.Berkeley.EDU was allowing any server to join the network without restriction. Troublemakers exploited this to attack users and channels. A group of operators, with Oikarinen's support, introduced "Q-lines" to quarantine themselves from eris, creating EFnet (Eris-Free Network). The original network effectively died.⁸

In October 1992, users who wanted to solve EFnet's growing problems with netsplits and channel takeovers created Undernet, introducing channel registration and protection services.⁸

In July 1996, a disagreement between European and American operators over how much power administrators should have led to the "Great Split." The European servers, including Finland where IRC was born, formed IRCnet. The American servers remained EFnet. The network that had connected the world split along the Atlantic.⁹

New networks continued to emerge: DALnet, QuakeNet, and eventually Freenode, which became the home of open source software development.

The Dark Side

IRC's openness made it a target.

The first IRC bot, Eggdrop, appeared in 1993 to help administrators manage channels.¹⁰ By the early 2000s, malware authors realized that IRC's simple, low-bandwidth protocol was perfect for something else: controlling botnets. Infected machines would connect to IRC channels and wait for commands.¹¹

Families like Back Orifice, Agobot, SDBot, and Dorkbot used IRC for command and control.¹² An attacker could type a command in an IRC channel and thousands of compromised machines would execute it simultaneously. DDoS attacks, spam campaigns, and credential theft all coordinated through the same protocol designed for Finnish students to chat.

IRC botnets still exist today, though many have migrated to Discord and Telegram.¹² The simplicity that made IRC accessible also made it exploitable.

Security on Port 6660

Plain-text IRC sends everything in the clear. Your nickname, your messages, your IP address. Anyone on the network path can read it all.

RFC 7194, published in 2014, standardized port 6697 for IRC over TLS/SSL.¹³ Modern IRC networks strongly encourage encrypted connections. If you're connecting to port 6660 today, you're likely using plain text.

The protocol has no built-in authentication for users. Services like NickServ (for nickname registration) and ChanServ (for channel protection) are add-ons, not part of the original specification. Security was not a priority in 1988. The Internet was a different place.

IRC Today

In 2021, Freenode, the largest IRC network and home to thousands of open source projects, experienced what many described as a hostile takeover. The network's volunteer staff resigned en masse and created Libera Chat. Within a week, Libera had processed 250 projects and 20,000 user registrations, calling themselves "the fastest-growing IRC network ever."¹⁴

Over a thousand projects migrated, including Arch Linux, FreeBSD, Gentoo, KDE, and the Wikimedia Foundation.¹⁵ The transition worked because IRC is an open protocol. You can point your client at a different server and keep talking. No company controls the protocol. No one can lock you in.

Today, Libera Chat has approximately 35,000 users. IRCnet has 18,000. EFnet has nearly 10,000. Over 2,000 IRC servers still operate worldwide.¹⁶

IRC may no longer dominate real-time chat. Discord and Slack have captured the mainstream. But IRC persists where its values matter most: in open source communities, among privacy-conscious users, and anywhere people want a chat system that no corporation can take away.

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