Indy

Internet Direct (Indy for short) is an open source Internet component suite comprised of popular Internet protocols. Indy is the most comprehensive socket library available for any language and contains support for TCP, UDP, ICMP, clients, servers, SMTP, POP3, IMAP4, HTTP, NNTP, FTP, and many more protocols. In fact Indy implements more than 120 protocols and Internet standards!

Indy is available for C#, Visual Basic.Net, Delphi, and Borland C++. Indy is also included in Borland's Delphi, Kylix, and C++ Builder.

http://www.indyproject.org/indy.html