The tools here were written to carry out cross-platform testing of the SO_LINGER socket option. You will find the results of our tests in the following blog posts:
https://www.nybek.com/blog/2015/03/05/cross-platform-testing-of-so_linger/
https://www.nybek.com/blog/2015/04/29/so_linger-on-non-blocking-sockets/
Our primary motivation for releasing the code is so that others can replicate the tests we carried out or test against new platforms.
The source code licensing here is a bit of a mess. The server tools, linger-server.c and win-linger-server.c, are released under the LGPLv3, and the client tool, linger-client.c, is released under the AGPLv3.
The code was developed for in-house research and in the process we borrows snippets of code from Michael Kerrisk's book, The Linux Programming Interface [2010]. In honouring the terms his code was released under we ended up with the aforementioned jumble of licenses.