Communication trough NAT.

what i need : 1) An iOs App with push notification , an edit box and send button. 2) A windows program , with 1 edit box and 1 textfield and 1 “Send Button” works like this : When I fire up the windows program , I want to be able to enter a text and press “Send”. The iOs app which is online continuously AND can be behind a NAT (on 3G connection) or at the internal WIFI network, receive this text and shows a notification on my iPhone. The iOs app will work the same way as the windows program. Instead of notification, the windowprogram will show a popup screen with the entered text. Important. • Communication in either way needs to react within 2 seconds. The notification on iOs device need to react within 2 seconds also. • I want a direct connection between both programs without a relay server. • Multiple iOs devices can be ‘linked’ to the windows program, all iOs devices will react in similar way and simultaniously.