TML Messaging Suite
Establishing asynchronous, multithreaded, bidirectional communication without blocking messages can be time consuming and error prone. Using libTML allows you to implement asynchronous message exchange on top of the IETF standard protocol BEEP (Blocks Extensible Exchange Protocol) without the need to fiddle around with the basics of message processing. All your work can be put into the features of the application instead of taming a TCP/IP socket.
Available as binary packages for Windows 32/64, FreeBSD, macOS and Linux.
It is Open Source. LGPL 2.1.