Thread: Push Notification Client/Server

OK people here are my "untested" Server classes to be run in the browser. Java Security says this stuff must be jarred and signed + permitted by system policy. The license is provided here in this post and only this post:

This code and this concept is FREE for ANYONE to do whatever IS DESIRABLE with IT. Only IT (the code and concept) may NOT be proposed to or granted Copyright to any individual or entity in an effort to PREVENT OR SUE anyone from employing similar technology in their projects and or products.

- Best damned free software license smokin' (BDF-SLS License as DEFINED HERE)

First a callback interface:

package web.site.push;
 
import java.net.InetAddress;
 
public interface Pushable {
 
	public void ServiceActivated(Listener service);
	public void ServiceTerminated(Listener service);
 
	public void DebugMessage(Listener service, String error);
	public void ConnectionRefused(Listener service, InetAddress from);
	public void Pushed(Listener service, InetAddress from, int operation, int flags);
 
}

This next class is the heart and soul of the 'daemon' which accepts connections from any 'registered' remote address. Local interface is registered automatically. Connection and data transfer processing is handled sequentially by a single thread that runs separate from the "user-space." This is the intended design to prevent race conditions from multiple remote sources (web servers) who intend to push notifications independently to a web client (this server). Once a notification has been processed, run errant, or denied, the remote connection is closed and the daemon returns processing the next incoming connection, provided that it has not been instructed to die. This "one-shot" technique is employed for the advantage of local concurrency and CGI programs who are themselves generally "one-shot" processes.

package web.site.push;
 
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.UnknownHostException;
import java.nio.ByteBuffer;
 
public class Listener implements Runnable {
 
	private int localPort = 0;
	private Pushable owner;
	private ServerSocket com;
	private Thread daemon;
	private InetAddress[] remoteClients;
	private static int listeners = 0;
	private int myRef = 0;
	private String myName = "";
 
	private boolean acceptable = false; // Accept another connection?
 
	public Listener(Pushable callback, String name) {
 
		owner = callback;
 
		// Set default accept from local host
		remoteClients = new InetAddress[1];
		try {remoteClients[0] = InetAddress.getLocalHost();} catch (UnknownHostException ex) {}
 
		daemon = new Thread(this);	// Declared here to allow access to IsAlive()
 
		ref();
 
		if (name == null || name.equals("")) { name = "" + myRef;}
		myName = name;
 
	}
 
	public void run() {
 
		owner.ServiceActivated(this);
 
		while (acceptable) {
 
			try {
				HandleConnection( com.accept() );
			}
 
			catch (IOException ex) { // System error....
				acceptable = false;	 // BREAK NEXT LOOP
				owner.DebugMessage(this, ex.toString()); // Report
			}
 
		}
 
		try {
 
			com.close();
 
		} catch (IOException ex) {
 
			owner.DebugMessage(this, ex.toString());
 
		}
 
		owner.ServiceTerminated(this);
 
	}
 
	private void ref() {
		listeners++;
		myRef = listeners;
	}
 
	public int ID() {
		return myRef;
	}
 
	public String Name() {
		return myName;
	}
 
	public InetAddress LocalAddress() {
		return com.getInetAddress();
	}
 
	public int LocalPort() {
		return com.getLocalPort();
	}
 
	public boolean Listen(int port) {
 
		// attempt to listen on all local interfaces
		return Listen(null, port);
 
	}
 
	public boolean Listen(InetAddress localAddress, int port) {
 
		if (daemon.isAlive()) { return true; }
 
		localPort = port;
 
		try {
 
		  com = new ServerSocket(localPort, 1024, localAddress);
 
		}
 
		catch (SecurityException se) {
 
			owner.DebugMessage(this, se.toString());
			return false;
 
		}
 
		catch (IOException ex) {
 
			owner.DebugMessage(this, ex.toString());
			return false;
 
		}
 
		daemon.start (	);
 
		return daemon.isAlive();
 
	}
 
	public void Die() {
 
		acceptable = false;
 
	}
 
	public boolean Listening() {
 
		return daemon.isAlive();
 
	}
 
	private void HandleConnection(Socket remote) {
 
		InputStream is;
		OutputStream os;
		byte[] in = new byte[8];
		ByteBuffer input = ByteBuffer.wrap(in);
 
		if (remote != null) {
 
			try {
 
				InetAddress fromAddress = remote.getInetAddress();
				os = remote.getOutputStream();
				is = remote.getInputStream();
 
				if (ConnectionPermitted(fromAddress)) {
 
					os.write(6);  // ASCII ACK
					os.write(22); // Synchronus idle
					os.flush();
 
					int count = 0;
					int loop = 0;
 
					while(true) {
 
						count = is.available();
 
						if (count == 8) {
							break;
						} else if (count > 8) { throw new IOException("Input past expected end of stream from: " + DescribeAddress(fromAddress)); }
 
						try { Thread.sleep(10); } catch (InterruptedException ex) { owner.DebugMessage(this, "Idle synchronization sleep interrupted."); }
 
						loop++;
 
						if (loop > 500) {
							// 5 second timeout or 500 repitions exceeded
							//os.write(22); // Synchronus idle
							os.write(21); // Not acknowledged (timed out)
							os.write(16); // Data link escape
							os.flush();
							throw new IOException("Synchronus idle timeout waiting for: " + DescribeAddress(fromAddress));
						}
					}
 
					is.read(in, 0, 8);
 
					int op = input.getInt();
					int ex = input.getInt();
 
					owner.Pushed(this, fromAddress, op, ex);
 
					os.write(6);  // Acknowledged
					os.write(16); // Data link escape
					os.flush();
 
				} else {
 
					// Connection not permitted.
					os.write(21); // Request not Acknowledged
					os.write(16); // Data link escape
					os.flush();
 
				}
 
			} catch (IOException ex) { owner.DebugMessage(this, ex.getMessage()); }
 
			try {remote.close();} catch (IOException ex) { owner.DebugMessage(this, ex.toString()); }
 
		}
 
	}
 
	public boolean ConnectionPermitted(InetAddress remote) {
 
		for (int i = 0; i < remoteClients.length; i++) {
 
			if (remoteClients[i].equals(remote)) {
 
				return true;
 
			}
 
		}
 
		owner.ConnectionRefused(this, remote);
 
		return false;
 
	}
 
	public static String DescribeAddress(InetAddress sa) {
		return sa.getHostName() + " (" + sa.getHostAddress() + ")";
	}
 
 
	public void AcceptClient(InetAddress client) {
		if (client == null) { return; }
		if (ConnectionPermitted(client)) { return; }
		InetAddress[] copy = remoteClients.clone();
		remoteClients = new InetAddress[copy.length+1];
		System.arraycopy(copy, 0, remoteClients, 0, copy.length);
		remoteClients[remoteClients.length - 1] = client;
	}
 
	public void DenyClient(InetAddress client) {
		if (client == null || remoteClients[0].equals(client) || remoteClients.length == 1) { return; }
		if (! ConnectionPermitted(client)) { return; }
		InetAddress[] newcopy = new InetAddress[remoteClients.length - 1];
		int offset = 0;
		for (int i = 0; i < remoteClients.length; i++) {
			if (! remoteClients[i].equals(client)) {
				newcopy[i+offset] = remoteClients[i];
			} else {
				offset = -1;
			}
		}
		remoteClients = newcopy.clone();
	}
 
}

As I stated in the beginning of this thread I basically have ZERO experience with java programming so there may be some stuff in this code that doesn't work properly, specifically the call to Thread.Sleep and the method I used to ensure that all data was available before the desired 8 bytes were read into the buffer. If you know much about socket programming and it looks shady to you, please feel free to post a fix. I couldn't find any examples of a server that operates this way.

Finally I provide the APPLET class which uses the NETSCAPE.JAR for Cross Browser LiveConnect Functionality. You must provide the MAYSCRIPT attribute to the applet's HTML definition or this code will fail you when attempting to get the browser window object or perform any callbacks from java to notify the "web client controller" scripts.

Even though the Listener class supports adding and removing remote connection permissions at runtime this functionality is not extended to the browser by this class for security reasons. All acceptable connections must be defined in HTML before the class's "init" method is called by the browser. All of these classes should be considered "conceptual" although they might even work out of the box or with just a few minor code edits. By design an HTML document may define as many listeners as the system it runs on will support.

Applet Code:

package web.site.push;
import java.applet.Applet;
import java.net.InetAddress;
import java.net.UnknownHostException;
import netscape.javascript.*;
 
public class Target extends Applet implements Pushable {
 
	private JSObject window = null;
 
	private String jsCallBackMethod = "onServerPush";
	private String jsDebugMethod = "";
	private String jsActivateMethod = "";
	private String jsTerminateMethod = "";
	private String jsRefusedConnectionMethod = "";
	private String jsObjName = "";
	private boolean useDebugging = false;
 
	private int listenerPort = 1982;
	private Listener listener = null;
 
	@Override
	public void init() {
 
		// get the JSObject representing the applet's browser window.
		window = JSObject.getWindow(this);
 
		// get initial config params if present
		String supplied = getParameter("onPush");
		if (supplied.length() > 0) {
			jsCallBackMethod = supplied;
		}
 
		supplied = getParameter("onDebug");
		if (supplied.length() > 0) {
			jsDebugMethod = supplied;
			useDebugging = true;
		}
 
		supplied = getParameter("debugging");
		if (supplied.equalsIgnoreCase("true") || supplied.equals("1")) {
			useDebugging = true;
		}
 
		supplied = getParameter("onActivate");
		if (supplied.length() > 0) {
			jsActivateMethod = supplied;
		}
 
		supplied = getParameter("onTerminate");
		if (supplied.length() > 0) {
			jsTerminateMethod = supplied;
		}
 
		supplied = getParameter("onConnectionRefused");
		if (supplied.length() > 0) {
			jsRefusedConnectionMethod = supplied;
		}
 
		supplied = getParameter("LocalPort");
		if(supplied.length() > 0) {
			listenerPort = Integer.parseInt(supplied);
		}
 
		supplied = getParameter("Name");
		if(supplied.length() > 0) {
			jsObjName = supplied;
		}
 
		listener = new Listener(this, jsObjName);
 
		supplied = getParameter("RemoteClients");
		if (supplied.length() > 0) {
			String[] clients = supplied.split("\\s+");
			for (int i = 0; i < clients.length; i++) {
				try {
					listener.AcceptClient(InetAddress.getByName(clients[i]));
				} catch (UnknownHostException ex) {
					DebugMessage(listener, "Unknown Host: " + clients[i]);
				}
			}
		}
 
		listener.Listen(listenerPort);
 
	}
 
	public void Pushed(Listener service, InetAddress from, int operation, int intent) {
		Object[] args = new Object[4];
		args[0] = service.Name();
		args[1] = from.getHostName();
		args[2] = operation;
		args[3] = intent;
		window.call(jsCallBackMethod, args);
	}
 
	public int LocalPort() { return listenerPort; }
 
	public void Terminate() {
		listener.Die();
	}
 
	public boolean Active() {
		return listener.Listening();
	}
 
	public void ConnectionRefused(Listener service, InetAddress from) {
 
		if (jsRefusedConnectionMethod.length() > 0) {
			Object[] args = new Object[3];
			args[0] = service.Name();
			args[1] = from.getHostName();
			args[2] = from.getHostAddress();
			window.call(jsRefusedConnectionMethod, args);
		} else {
			DebugMessage(service, "Connection Refused from: " + from.getHostName() + " (" + from.getHostAddress() + ")");
		}
 
	}
 
	public void DebugMessage(Listener service, String msg) {
 
		if (! useDebugging ) { return; }
 
		if (jsDebugMethod.length() > 0) {
			Object[] arg = new Object[2];
			arg[0] = service.Name();
			arg[1] = msg;
			window.call(jsDebugMethod, arg);
		} else {
			System.err.println("Push Listener (" + service.Name() + "): " + msg);
		}
 
	}
 
	public void ServiceTerminated(Listener service) {
		if (jsTerminateMethod.length() > 0) {
			Object[] arg = new Object[2];
			arg[0] = service.Name();
			arg[1] = "Service Terminated";
			window.call(jsTerminateMethod, arg);
		} else {
			DebugMessage(service, "Service Terminated");
		}
	}
 
	public void ServiceActivated(Listener service) {
		if (jsActivateMethod.length() > 0) {
			Object[] arg = new Object[2];
			arg[0] = service.Name();
			arg[1] = "Service Activated";
			window.call(jsActivateMethod, arg);
		} else {
			DebugMessage(service, "Service Terminated");
		}
	}
 
}

Ok that's it for the web-client server! Hopefully my next post will contain a complete zipped working example of a client/server as well as a textual code listing of the client class as was presented here in this post with the above classes.

According to my own specification, this is a:

Private Application Push Notification Service

Ahh yes its a wonderful day.. I was so tired yesterday after my 14 hour non-stop shift working on the above classes I failed to see just how simple a client that employs this service really is. So how do I intend to make this service useful across many machines, server-side technologies and architectures? The answer is simple: JAVA!

Most server-side technologies have access to the command line interface. Thusly I have written a very arcane class to provide CLI access to the TWO-PROCEDURE class that is the client.

NOTICE: Before you use this class, you should note that line 183 in web.site.push.Listener (in post #5) was recently updated (commented out) to work with this client. This client expects only two bytes of status information. The previous code provided 3.

Ladies and Gentleman, I give you web.site.Push:

package web.site;
 
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.Socket;
import java.net.UnknownHostException;
import java.nio.ByteBuffer;
 
public class Push {
 
	public static int Notice(String host, int port, int operation, int flags) {
 
		int errCode = 0;
 
		byte[] in = new byte[2];
		byte[] out = new byte[8];
 
		ByteBuffer writer = ByteBuffer.wrap(out);
 
		writer.putInt(operation);
		writer.putInt(flags);
 
		try {
 
		  Socket remote = new Socket(host, port);
 
		  InputStream is = remote.getInputStream();
 
		  is.read(in, 0, 2);
 
		  if (in[0] == 6 && in[1] == 22) { // Server is waiting for input!
 
			OutputStream os = remote.getOutputStream();
			os.write(out);
			os.flush();
			is.read(in, 0, 2);
 
			if (in[0] == 21) { // we timed out!
				System.err.println("Remote notification failed to synchronize: " + host + encase(port));
				errCode = 4;
			}
 
		  } else { errCode = 3; } // our input was rejected :(
 
		  remote.close();
 
		}
 
		catch (UnknownHostException ex) { // we couldn't connect!
 
		  System.err.println(ex);
		  return 1;
 
		}
 
		catch (IOException ex) { // something seriously screwed up..
 
		  System.err.println(ex);
		  return 2;
 
		}
 
		return errCode;
 
	}
 
	private static String encase(int num) {
		return " (" + num + ")";
	}
 
}

Pretty straight-forward and self documenting I might add. And finally a CLI to allow shell access to CGI programs and scripts web.site.cli.Notify:

package web.site.cli;
 
public class Notify {
 
	public static void main(String[] args) {
 
		if (args.length != 4) {
			System.err.println("Error: expected 4 arguments {Basic notation: $host %port %command %flags} (Java notation: String int int int)");
			System.exit(5);
		}
 
		System.exit(web.site.Push.Notice(args[0], Integer.parseInt(args[1]), Integer.parseInt(args[2]), Integer.parseInt(args[3])));
 
	}
 
}

Unfortunately, I still have not had the oppertunity to test any of these classes. But this is a solid concept presented here. I also wanted to add some examples however I believe from a beginners point of view all of this software is self explanatory provided you are educated in the underlying technologies. The CLI itself explains pretty fairly how to use the client. Some HTML to define a listener would look something like this:

HTML Code:

<applet id="listener" code="web.site.push.Target" archive="web-tools-signed.jar"
 style="width: 0px; height: 0px; float: left;" mayscript>
<param name="Name" value="listener">
<param name="LocalPort" value="2011">
<param name="onPush" value="listeners_Push">
<param name="onDebug" value="listeners_Debug">
<param name="onActivate" value="listeners_Activate">
<param name="onTerminate" value="listeners_Terminate">
<param name="onConnectionRefused" value="listeners_ConnectionRejected">
<param name="RemoteClients" value="myhost.somesite.com myhost2.it 249.148.127.100">
</applet>

Access to the public methods of the applet are considered trivial here. If more information is required consult any tutorial on: LiveScript (java/javascript intermingling for web browsers)

For all practical purposes and intents, I will supply the JS method signatures for your convenience.

HTML Code:

<script>
function listeners_ConnectionRejected(ServiceName, RemoteHostName, RemoteIP) {}
function listeners_Terminate(ServiceName) {}
function listeners_Activate(ServiceName) {}
function listeners_Debug(ServiceName, MessageText) {}
function listeners_Push(ServiceName, RemoteHostName, DesiredOperation, Flags) {}
</script>

If this concept is not an example you can follow with logic you might be in the wrong forum! However I will answer any meaningful questions directed at me about this software/concept. I am no java Guru so don't expect me to discuss JVM execution philosophy or something else that really has nothing to do with this software/concept.

If you will run from the server side using something like

perl/php/bash/basic/js/BATCH/vbscript/Visual Basic/Wscript/Assembler/C/C#/C++/.NET

you will need to learn about running shell commands and capturing STDERR by using redirects to a file or simply using some method to capture the stream to a variable. You will also need to study how to build a java command line application to allow the CLI Notification class to be executed by the java command.

{String Host} {int Port} {int Operation} {int Flags}

These are the four fields the Command Line Interface program expects to find as arguments. If more or less are found an error is "thrown" and the application will exit with a status code of 5. If the operation is successful status code will be zero. Codes 1-4 are defined (in code as return values) within the web.site.Push class.

If you have any questions about the JavaScript Method Signatures please consult the web.site.push.Target method that calls each of them respectively. If you are using JSP you only need to call the Static method Notice located in web.site.Push refer to the CLI class for more information.

web.site.Push.Notice(String host, int port, int operation, int flags);

Have a great day, and please be sure to inform myself and others of your progress or findings!