I have found the reason for SocketEception. It was server firewall restiction. It is important to open this ports:
■TCP port 5223 (used by devices to communicate to the APNs servers)
■TCP port 2195 (used to send notifications to the APNs)
■TCP port 2196 (used by the APNs feedback service)
■TCP Port 443 (used as a fallback on Wi-fi only, when devices are unable to communicate to APNs on port 5223)
After opening all of the ports everthing was alright. I hope that someone can use this info!