Hiawatha is a secure and advanced Web server for Unix. It has been written with security as its main goal. It features advanced access control, prevention of SQL injection and cross-site scripting, banning of clients who try such exploits, the ability to run CGIs under any UID/GID you want, and many other features. These features make Hiawatha an interesting Web server for those who need more security than what the other available Web servers are offering. Hiawatha is also fast and easy to configure.
Higgs.IO is a high performance, message oriented network library built for realtime systems. It provides a core extensible framework and libraries built on top of the core. Libraries include a WebSocket server, an HTTP server and client, and Boson, a custom serialization and RMI library.
HttpdBase4J is an embeddable Java Web server framework that supports HTTP, HTTPS, templated content, and serving content from inside an archive or from the classpath. The classes are easy to extend as they utilize the "don't call us, we'll call you" principle to allow the user to override the framework behavior during all the different phases of the HTTP transaction.
Hydra is a high performance multi-threaded HTTP server. Unlike traditional multi-threaded Web servers, it uses a constant, configurable pool of threads, and each thread can handle several connections by multiplexing the connections. This is even better than non-blocking servers, since Hydra will use every available CPU in a multi-CPU system. It also has features such as host-based virtual hosting, HTTP 1.1 features, CGI 1.1, SSL 3.0, TLS 1.0, and more. Hydra was based on the Boa Web server.