JS-Collider is an event-driven Java network NIO framework. It is designed to provide maximum performance and scalability for applications having not too many connections but significant amounts of network traffic (both incoming and outgoing). Performance and scalability are achieved via lock free algorithms and atomic states usage. It supports UDP (with multicast) as well. One of the implementation points is to avoid unsafe cheating; it should work the same way on all JVMs (Java 1.7). It supports shared memory IPC.
trx is a toolset for broadcasting live audio from Linux. It sends and receives encoded audio over IP networks, via a soundcard or audio interface, and can be used for point-to-point audio links or multicast (e.g., private transmitter links or audio distribution). High-quality wideband audio (such as music) can be sent with low latency and fast recovery from dropouts.
s6-networking is a collection of small Unix tools designed to help networking. It includes clock synchronization, Unix and TCP super-servers, Unix and TCP access control, and other miscellaneous utilities. It is particularly suited for management of clients and servers on embedded devices, but works just as well on larger systems.