package examples.example2_one_client_OO;
import java.io.BufferedReader;
import java.io.Closeable;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.InetAddress;
import java.net.Socket;
import javax.swing.JOptionPane;
/**
* <pre>
* NetworkingExamples project: examples.example2_one_client_OO.
*
* A simple example of networking (Sockets) in which:
* -- A single Server and Client exchange information, one after the other.
*
* This is the Client code.
*
* This is the same example as {@link examples.example1_one_client}
* except structured in a more OO way. In particular, this structure has 3 classes:
* -- Main: for starting the program.
* -- Server: for initiating and running the Server.
* -- Client: for initiating and running the Client.
*
* See {@link examples.example1_one_client#MainForServer} for:
* -- Exactly what information the Server and Client exchange in this demo.
* -- The 7 Key Statements that are all-you-need-to-know to do networking in Java.
*
* See {@link examples.example3_one_client_OO_library} for this same example
* but using the simple networking library in package {@link simpleNetworking}.
* </pre>
*
* @author David Mutchler, based on the Java Tutorials on networking. May, 2009.
*/
public class Client implements Runnable {
private BufferedReader in;
private PrintWriter out;
private Socket socketToCommunicateWithServer;
/**
* <pre>
* Constructs readers and writers for talking to the Server, as follows:
*
* 1. Constructs a Socket to the Server, using the given hostname and port.
* Note: The Server must be accepting clients at this point,
* else the construction of the Socket by this Client will fail.
*
* 2. Use that Socket to:
* a. Get an InputStream. Then decorate the InputStream
* into a BufferedReader (for more efficient communication).
* b. Get an OutputStream. Then decorate the OutputStream
* into a PrintWriter (for convenient ways to write messages).
*
* Finally, this constructor:
* 3. Starts a Thread in which the Client repeatedly communicates with the
* Server (so that you can see a simple example of network communication).
* </pre>
*
* @param hostName HostName or IP address of the Server to which to connect.
* @param port Port to use for the Socket that connects to the Server
* at the given hostName.
* @throws Throwable if any Exception or Error occurs.
*/
public Client(String hostName, int port) throws Throwable {
try {
//-------------------------------------------------------------------------------------
// KEY #7: Connect to the given Server, getting a Socket for communicating with it.
this.socketToCommunicateWithServer = new Socket(hostName, port);
//-------------------------------------------------------------------------------------
//-------------------------------------------------------------------------------------
// From the Socket, construct a BufferedReader for reading from the Client.
this.in = new BufferedReader(new InputStreamReader(
this.socketToCommunicateWithServer.getInputStream()));
//-------------------------------------------------------------------------------------
//-------------------------------------------------------------------------------------
// From the Socket, construct a PrintWriter for writing to the Client.
this.out = new PrintWriter(
this.socketToCommunicateWithServer.getOutputStream(), true);
//-------------------------------------------------------------------------------------
new Thread(this).start();
} catch (Throwable exception) {
this.close();
throw exception;
}
}
/**
* <pre>
* A simple example of communication between this Client and the Server.
*
* It behaves as follows:
*
* Initiate the protocol by sending a random number to the Server. Then:
*
* Repeatedly, until the Server sends STOP or the user says to stop:
* -- Get a number from the Server.
* -- Add a random number between 0 and 10 to it.
* -- After pausing 0 to 5 seconds, send the revised number to the Server.
*
* The Server can send whatever number it wishes at each iteration;
* in fact, the particular Server in this program takes the number
* that the Client sends it, asks the user for another number,
* and sends the sum of the two numbers back to this Client.
*
* If the user says to stop, the Client sends a STOP message to the Server
* so that the Server will stop too.
* </pre>
*/
@Override
public void run() {
try {
//-------------------------------------------------------------------------------------
// Now start communicating with the Server.
//-------------------------------------------------------------------------------------
int number;
String dataFromServer;
int dataFromUser;
JOptionPane.showMessageDialog(null,
"This Client is running on "
+ InetAddress.getLocalHost().getCanonicalHostName() + "\n"
+ "which is IP address "
+ InetAddress.getLocalHost().getHostAddress() + "\n\n");
number = (int) (Math.random() * 100);
JOptionPane.showMessageDialog(null,
"The Client starts the ball rolling with the random number " + number);
//-----------------------------------------------------------------------------
// Write to the Server.
this.out.println(number);
//-----------------------------------------------------------------------------
while (true) {
//-----------------------------------------------------------------------------
// Read from the Server.
dataFromServer = this.in.readLine();
//-----------------------------------------------------------------------------
if (dataFromServer.equals("STOP")) { // Server says to stop.
JOptionPane.showMessageDialog(null,
"Client ended because the Server asked it to do so");
break;
}
number = (int) (Math.random() * 10); // What the Client does in this example.
dataFromUser = JOptionPane.showConfirmDialog(
null,
"The Client got " + dataFromServer + " from the Server.\n\n"
+ "The Client chooses to add " + number + " to the above.\n\n"
+ "Thus the Client will send "
+ (number + Integer.parseInt(dataFromServer))
+ " to the Server after a few seconds pause.\n\n"
+ "Press OK to continue or Cancel to quit this program.\n\n",
"Continue?",
JOptionPane.OK_CANCEL_OPTION);
System.out.println(dataFromUser);
if (dataFromUser == JOptionPane.CANCEL_OPTION) {
// User selected Cancel in input dialog.
JOptionPane.showMessageDialog(null,
"Client ended because the user asked it to do so.\n\n"
+ "Tell the Server to stop too.\n\n");
this.out.println("STOP"); // Tell the Server to stop
break; // and stop this Client.
}
Thread.sleep((long) (Math.random() * 5000));
//-----------------------------------------------------------------------------
// Write to the Server.
this.out.println(number + Integer.parseInt(dataFromServer));
//-----------------------------------------------------------------------------
}
} catch (IOException exception) {
System.out.println(exception);
JOptionPane.showMessageDialog(null,
"Client ended, probably because the user closed the Server.\n\n");
}
catch (Throwable exception) {
System.out.println(exception);
JOptionPane.showMessageDialog(null, "Client ended abnormally. See stack trace.");
exception.printStackTrace();
}
this.close();
}
/**
* Closes all resources that this Client uses: writer, reader, socket.
*/
void close() {
Closeable[] resourcesToClose = {this.out, this.in};
JOptionPane.showMessageDialog(null, "Closing the client's resources.");
for (Closeable resource : resourcesToClose) {
try {
resource.close();
} catch (Exception exception) {
// Ignore; we made our best effort at closing the resource.
}
}
try {
this.socketToCommunicateWithServer.close();
} catch (Exception exception) {
// Ignore; we made our best effort at closing the resource.
}
}
}