TwIRC

The IRC protocol is a solid, tried and tested, decades old protocol that's still popular to this day. If you need chat in your project, why reinvent the wheel? Instead go with something that just works!
TwIRC is a highly customizable, easy to use IRC client package for Unity. With it you can do anything, from using it as the backbone for your MMO's chat system, connecting your players to their stream viewers, or even make a bot for whatever purpose you may have!
Windows Demo | Forum
Network Code Features:
• Supports all common message types/events.
• CTCP protocol support.
• Multi-Threaded. No freezing!
• Auto reconnect.
• Easy to use with any UI!
• No dlls! Fully customizable code!
• Uses Sockets. Supports most platforms (WebGL excluded).
Interface Features:
• Easy customizable setup.
• Customize slash commands for each message type and channel.
• mIRC color code support.
• Tabbed MMO interface, starter template using the modern 5.6+ UI.
• Twitch support.
• Supports multiple channels.
Included Demos:
• MMO Chat System template/example.
• Inspector Editor UI example.
CTCP Protocol support includes:
• Action.
• Ping.
• Version.
• ClientInfo.
• Source.
• Time.