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:
Our primary motivation for releasing the code is so that others can replicate the tests we carried out or test against new platforms.
About the licensing:
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 . In honouring the terms his code was released under we ended up with the aforementioned jumble of licenses.