SuperSocket is a light weight extensible socket application framework. You can use it to build a command based server side socket application (like FTP server, SMTP/POP3/IMAP4 server, SIP server, etc) easily without thinking about how to use socket, how to maintain the socket connections and how socket works(synchronize/asynchronize). It is a pure C# project which is designed to be extended, so it is easy to be integrated to your existing system. As long as your systems (like forum/CRM/MIS/HRM/ERP) are developed in .NET language, you must be able to use SuperSocket to build your socket application as a part of your current system perfectly.
Go to http://supersocket.codeplex.com/
See also these related projects.