...
For Jetty 7.5+ this is
<filter-class>org.apache.wicket.protocol.httpws.jetty7.Jetty7WebSocketFilter</filter-class>
For Tomcat 7.0.27+:
<filter-class>org.apache.wicket.protocol.ws.httptomcat7.Tomcat7WebSocketFilter</filter-class>
...
...
For Jetty 7.5+ this is
<filter-class>org.apache.wicket.protocol.httpws.jetty7.Jetty7WebSocketFilter</filter-class>
For Tomcat 7.0.27+:
<filter-class>org.apache.wicket.protocol.ws.httptomcat7.Tomcat7WebSocketFilter</filter-class>
...