Soup is a SOAP (Simple Object Access Protocol) implementation in C. 

It provides an queued asynchronous callback-based mechanism for sending and
servicing SOAP requests, and a WSDL (Web Service Definition Language) to C
compiler which generates client stubs and server skeletons for easily calling
and implementing SOAP methods.

It uses the GLib main loop and is designed to work well with GTK applications.

Features:
  * Completely Asynchronous
  * Connection cache
  * HTTP chunked transfer and persistent connections
  * authenticated HTTP, SOCKS4, and SOCKS5 proxy support
  * SSL Support using OpenSSL
  * Apache module server support
  * Client digest authentication