how to maintain a connexion to send realtime data to distant client without request - sockets

Question

i'm developing a mobile project the can control a home an receve information from it either from inside or outside of the house. im setting up a port forwarding mechanism on my router to connect to my server if i'm using my application from the outside.
i think that the fact of receving data from the server should be initiated by the client (android app) witch is in an other notwork or it will be blocked.
* is there a solution to receve data (temperature) in real time from the outside simply by just requesting once or i should send a request like evrey minute? * i'm confused because some applications like video streaming receve data from servers by just starting the video player then it receve udp packets automaticly
more spicificlly can i send data from a server to a distant client by just sending a request once (maybe by letting the socket open for every client, VPN , SIP)???

Answer 1

Sending Data to Distant Clients: Securely & Reliably
There is only one reasonably-reliable method for sending a signal to distant clients. I want to confirm your original assumption of sending to clients without request, this is theoretically impossible as the device needs to call home somewhere and notify a broker gateway (SIP) or otherwise of it's address. However please ignore that because the right way will be relayed here with source code.
Security Importance
It is important to realize that opening your firewall is outside of good practices. It is better to hold onto the firewall's lockdown rules for inbound traffic. The following section is a secure method that will allow you to open an outbound connection with maximum security preventing snooping and other unsafe security holes.
Download Android Source Libraries
See instructions here for downloading Android Source Library Files: https://github.com/pubnub/java/tree/master/android
Receiving Data On-Demand from a Distance on Android
You'll need to copy/paste the following code to get things moving forward quickly. Start by taking this Java code and pasting it into your app. Then follow by downloading the library files.
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
// ANDROID PHONE
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Pubnub pubnub = new Pubnub(
"", // PUBLISH_KEY (Optional, supply "" to disable)
"demo", // SUBSCRIBE_KEY (REQUIRED)
"", // SECRET_KEY (Optional, supply "" to disable)
"", // CIPHER_KEY (Optional, supply "" to disable)
true // SSL_ON?
);
Hashtable args = new Hashtable(1);
args.put( "channel", "distant-client-ABC-DEF" );
pubnub.subscribe(args, new Callback() {
public void connectCallback(String channel) {
System.out.println("CONNECT on channel:" + channel);
}
public void disconnectCallback(String channel) {
System.out.println("DISCONNECT on channel:" + channel);
}
public void reconnectCallback(String channel) {
System.out.println("RECONNECT on channel:" + channel);
}
public void successCallback(String channel, Object message) {
System.out.println(channel + " " + message.toString());
}
public void errorCallback(String channel, Object message) {
System.out.println(channel + " " + message.toString());
}
});
Send Data On-demand to the Distant Client
On a Java VM on your home computer/systems, you may use the same code to send data securely to the remote distant client. Use the following code to do this:
Download JVM Server Source Libraries
See instructions here for downloading/using JVM Server Source Library Files: https://github.com/pubnub/java/tree/master/java
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
// HOME SERVER
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Pubnub pubnub = new Pubnub(
"demo", // PUBLISH_KEY (REQUIRED on Server)
"demo", // SUBSCRIBE_KEY (REQUIRED)
"", // SECRET_KEY (Optional, supply "" to disable)
"", // CIPHER_KEY (Optional, supply "" to disable)
true // SSL_ON?
);
Hashtable args = new Hashtable(1);
args.put( "channel", "distant-client-ABC-DEF" ); // SEND TO CLIENT ABC-DEF
pubnub.publish(args, new Callback() {
public void successCallback(String channel, Object message) {
System.out.println("PUBLISH : " + message);
}
public void errorCallback(String channel, Object message) {
System.out.println("PUBLISH : " + message);
}
});

Answer 2

I'm not into Android world, but isn't it the service you're looking for ? : http://developer.android.com/google/gcm/index.html