Components and Libraries Websites

HTTrack is a free (libre/open source) and easy-to-use offline browser utility. Source code is available for Windows and Linux/Unix/BSD.

Object-oriented Internet library for Xbase++. Includes classes for TCP/IP socket communications, HTTP, SOAP, SMTP, POP3, FTP. [Commercial]

PINPI is a programming interface based on an all-purpose platform independent networking protocol and data format (SDXF, the Structured Data eXchange Format)for use to realize client/server (or similar) applications.

Libwww is a highly modular, general-purpose client side Web API written in C for Unix and Windows (Win32).

Sockets library for UNIX platforms that looks much like regular C-style i/o. [Open Source, Free]