The serf library is a high performance C-based HTTP client library built upon
the Apache Portable Runtime (APR) library. It is permissively licensed under
the Apache License, v2.

Key features:
* multiplexed, asynchronous connections,
* SSL/TLS support,
* full HTTP pipelining,
* multiple authentication modes (Basic, Digest, Kerberos/NTLM),
* zero-copy support for increased throughput.