A simple alternative to the STL plus portable multithreading and networking. Compiles under modern Unix and Windows systems. [Open-source, zlib-like license]

A socket based communications library for use in a multi-tiered environment. [OPen source, LGPL]

A Java component for accessing sockets via ColdFusion.

EzSocket provide an easy way to write server and client programs that make use of stream sockets. [Open source, LGPL]

With the HTTPort SDK you can make the Internet software you write working from behind an HTTP proxy. Demo version includes binary code and samples in C, Visual Basic and Delphi.

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

Network library for Linux, Windows, FreeBSD and Solaris providing sniff, spoof, packet creation, packet decoding, packet printing, and address conversion. [Open Source, Free]

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

Netwib provides client, server and most functions needed by network programs.

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.

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

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