I haven't tried primefaces-push but I just use Atmosphere (primefaces-push is using Atmosphere too). To make it work I have to add those JVM options:
-Dv3.grizzly.cometSupport=true
-Djava.net.preferIPv4Stack=true
(I am not sure if this option is still required with the last versions of Atmosphere)
Maybe it could help you.