application server
software framework that provides both facilities to create web applications and a server environment to run them
Tuxedo
software
Novell exteNd
web application development suite
Open Liberty
application server runtime environment
Mongrel
HTTP library and web server
Unicorn
HTTP server for Ruby
Puma
web server software
Oracle Application Server
integrated, standards-based software platform
Apache Tomcat
an implementation of the Java Servlet, JavaServer Pages, Java Expression Language and Java WebSocket technologies
RoadRunner
open-source application server, load-balancer, and process manager