look at the five basic models mentioned in the network programming book:

1. blocking IO
2. nonblocking IO
3. IO multiplexing
4. signal driven IO
5. asynchronous IO

I know that select/poll belongs to the third category, so which is the nodejs, tornado, gevent, in web server and the gunicorn that runs directly?
SQL server, which is the redis server?

if not all are sure, you are more than welcome to answer only one or some of them.