Sorry it took so long to address this issue.
Tomcat 9 has some architecture changes in respect to Tomcat 7, including the retirement of the custom Comet API, which we were using, in favor of the standard Java WebSocket.
It also means upgrading from Servlet 3.0 to Servlet 4.0 for asynchronous processing.
Given these significant changes, we have just created a new major version
3.0.0, which we’ll announce stable after giving some time to ensure everything works smoothly.
