Emcast is a multicast toolkit for distributed/peer-to- peer applications that require multicast communication. It includes the program "emcast", a generic multicast utility (like netcat), and the library "libemcast", a generic multicast library. Emcast supports IPv4 multicast (IM) and can easily support almost any end-host multicast (EM) protocol. The EM protocols supported are Banana Tree Protocol (BTP) and Internet Relay Chat (IRC).
GNet is a network library. It is object-oriented, written in C, and built upon GLib. It is intended to be easy to use and port. It supports abstract Internet addresses, TCP, UDP, IP Multicast, IPv6, asynchronous DNS lookups, SHA, MD5, Base64, URIs, and SOCKS. It comes with documentation and examples.