Should the connection be established in a separate java class of the program?
Yes. One java class should be sufficient to establish the connection, send messages to the beagleboard, and receive responses.
I assume I should establish a connection through the port with the device and send the requests for the info as the user requests.
Yes. You would format the requests in whatever format the beagleboard requires.
Here's a class I put together to make sure a single instance of the Java application ran. You would modify this for your communications.
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.UnknownHostException;
public class ApplicationInstanceManager {
private static final boolean DEBUG = false;
private static ApplicationInstanceListener subListener;
/** Randomly chosen, but static, high socket number */
public static final int SINGLE_INSTANCE_NETWORK_SOCKET = 44331;
/** Must end with newline */
public static final String SINGLE_INSTANCE_SHARED_KEY = "$$RabidNewInstance$$\n";
/**
* Registers this instance of the application.
*
* @return true if first instance, false if not.
*/
public static boolean registerInstance() {
// returnValueOnError should be true if lenient (allows app to run on
// network error) or false if strict.
boolean returnValueOnError = true;
// try to open network socket
// if success, listen to socket for new instance message, return true
// if unable to open, connect to existing and send new instance message,
// return false
try {
final ServerSocket socket = new ServerSocket(
SINGLE_INSTANCE_NETWORK_SOCKET, 10, InetAddress
.getLocalHost());
if (DEBUG)
System.out.println("Listening for application instances on socket "
+ SINGLE_INSTANCE_NETWORK_SOCKET);
Thread instanceListenerThread = new InstanceListenerThread(socket);
instanceListenerThread.start();
// listen
} catch (UnknownHostException e) {
EclipseLogging.logError(RabidPlugin.getDefault(),
RabidPlugin.PLUGIN_ID, e);
return returnValueOnError;
} catch (IOException e) {
return portTaken(returnValueOnError, e);
}
return true;
}
private static boolean portTaken(boolean returnValueOnError, IOException e) {
if (DEBUG)
System.out.println("Port is already taken. "
+ "Notifying first instance.");
try {
Socket clientSocket = new Socket(InetAddress.getLocalHost(),
SINGLE_INSTANCE_NETWORK_SOCKET);
OutputStream out = clientSocket.getOutputStream();
out.write(SINGLE_INSTANCE_SHARED_KEY.getBytes());
out.close();
clientSocket.close();
System.out.println("Successfully notified first instance.");
return false;
} catch (UnknownHostException e1) {
EclipseLogging.logError(RabidPlugin.getDefault(),
RabidPlugin.PLUGIN_ID, e);
return returnValueOnError;
} catch (IOException e1) {
EclipseLogging
.logError(
RabidPlugin.getDefault(),
RabidPlugin.PLUGIN_ID,
"Error connecting to local port for single instance notification",
e);
return returnValueOnError;
}
}
public static void setApplicationInstanceListener(
ApplicationInstanceListener listener) {
subListener = listener;
}
private static void fireNewInstance() {
if (subListener != null) {
subListener.newInstanceCreated();
}
}
public static void main(String[] args) {
if (!ApplicationInstanceManager.registerInstance()) {
// instance already running.
System.out.println("Another instance of this application " +
"is already running. Exiting.");
System.exit(0);
}
ApplicationInstanceManager
.setApplicationInstanceListener(new ApplicationInstanceListener() {
public void newInstanceCreated() {
System.out.println("New instance detected...");
// this is where your handler code goes...
}
});
}
public static class InstanceListenerThread extends Thread {
private ServerSocket socket;
public InstanceListenerThread(ServerSocket socket) {
this.socket = socket;
}
@Override
public void run() {
boolean socketClosed = false;
while (!socketClosed) {
if (socket.isClosed()) {
socketClosed = true;
} else {
try {
Socket client = socket.accept();
BufferedReader in = new BufferedReader(
new InputStreamReader(client.getInputStream()));
String message = in.readLine();
if (SINGLE_INSTANCE_SHARED_KEY.trim().equals(
message.trim())) {
if (DEBUG)
System.out.println("Shared key matched - "
+ "new application instance found");
fireNewInstance();
}
in.close();
client.close();
} catch (IOException e) {
socketClosed = true;
}
}
}
}
}
}
