A cross-platform C++ library for network and low-level I/O programming that provides developers with a consistent asynchronous model using a modern C++ approach.

A free C++ Web Development Framework aimed for Rapid Web Application Development which is designed and tuned to handle extremely high loads and uses modern C++ as primary development language. [Open Source, LGPL]

Provides synchronous send and receive of a buffer, plus ping and resolve address. The class encapsulates a listener thread which can be started and stopped.

A portable C++ Jabber/XMPP library which takes care of the low-level protocol stuff. Additionally, it offers high-level interfaces for interaction with an XMPP server. [Open Source, GPL]

An object-oriented, cross-platform C++ library which provides handling logic for the Jabber protocol. [Open Source]

A free implementation of XML-RPC in C++. It supports multithreading, secure connections and interceptors. [Open Source, LGPL]

A C++ wrapper for libpcap (the packet capture library), which provides a high level interface to packet capture systems. [Open Source, GPL]

Provides a simple to use interface for creating and using client sockets. Can connect to the destination server through an unlimited number of chainable proxies, SOCKS4 and SOCKS5 servers if anonymity or security is a priority. Supports SSL as well as normal connections. [Open Source, GPL]

A simple and lightweight C++ network sockets wrapper for Windows and Linux which is designed for games.

A collection of light-weight C++ classes which help to create a select-based event-driven applications, especially simple TCP servers and clients. [Open Source, LGPL]

A C++ library making socket based client/server programming easier.

A server framework library written on C++ that implements the Half-Sync/Half-Async and Leader/Follower patterns. It is a hybrid system between threaded and event-driven, and exploits the advantages of both programming models. It exposes a threaded programming style to programmers, while simultaneously using event-driven style to process network connection. [Open Source, LGPL]

A C++ class library for working with MIME messages and Internet messaging services like IMAP, POP or SMTP. [Open Source, GPL]