NBD — Network Block Device — is a protocol for accessing Block Devices
(hard disks and disk-like things) over a Network.
This is the NBD client library in userspace, a simple library for
writing NBD clients.
The key features are:
* Synchronous and asynchronous APIs, both for ease of use and for
writing non-blocking, multithreaded clients.
* High performance.
* Minimal dependencies for the basic library.
* Well-documented, stable API.
* Bindings in several programming languages.
