Indy
Indy is an open source client/server communications library that supports TCP/UDP/RAW sockets, as well as over 100 higher level protocols including SMTP, POP3, IMAP, NNTP, HTTP, FTP, and many more. Indy is written in Delphi but is available for C++Builder, Delphi, FreePascal, .NET, and Kylix.
http://www.indyproject.org
https://github.com/IndySockets/Indy