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COM561S2 - Concurrent and Distributed Computing (15-16)
Assignment 2
SOLUTIONS
Solution 1
(a) Single Threaded Client/Server System has the following interaction:
 Server waits for connections from clients
 When connection made the server sends a message to the client
prompting for the student number
 Client user types in the student number and sends it to the server.
 Server reads the student number and searches the list of records for
associated Student name and results.
 Student name and results are forwarded to the client, who reads and
displays them (if the student number is invalid this is indicated to the
client).
 The Client can keep requesting student details until it terminates the
communication by entering the value -1.
 The Server waits for the next client to connect.
UML Diagram - Client and Iterative Server
The client code consists of one class StudentAdminClient in a separate project with a JAR
file of StudentDetailsType in the Libraries folder.
import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.InputStreamReader;
import java.io.ObjectInputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
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import java.net.Socket;
import studentdetailstype.StudentDetailsType;
public class StudentAdminClient {
public static void main(String[] args) {
String hostName = "localhost"; // default host name
int hostPort = 4444; // default host port
// assign host machine name and port to connect to
if (args.length != 0) {
if (args[0] != null) {
hostName = args[0]; // user specified machine
}
if (args[1] != null) {
hostPort = Integer.parseInt(args[1]); // user specified port
}
}
System.out.println("Tyring to Connect to Student Admin Server");
// connect to server and extract input and output streams
try (Socket serverSocket = new Socket(hostName, hostPort);
PrintWriter os = new PrintWriter(new BufferedWriter(new
OutputStreamWriter(serverSocket.getOutputStream())));
ObjectInputStream is = new ObjectInputStream(new
BufferedInputStream(serverSocket.getInputStream()))) {
// read and display opening message from server
System.out.println("Server: " + is.readObject());
// create client input stream
BufferedReader userInput = new BufferedReader(new InputStreamReader(System.in));
System.out.print("Enter student number (-1 to quit): ");
String message = userInput.readLine();
while (!message.equals("-1")) {
sendMessageToServer(os, message);
handleResponse((StudentDetailsType)is.readObject());
System.out.print("Enter student number (-1 to quit): ");
message = userInput.readLine();
}
// sent termination request to server
sendMessageToServer(os, message);
// read closing message from server and display it
System.out.println(is.readObject());
} catch (Exception e) {
System.err.println("Exception: " + e.getMessage());
}
}
public static void sendMessageToServer(PrintWriter os, String msg)
{
os.println(msg);
os.flush();
}
public static void handleResponse(StudentDetailsType sDetails) {
// attempt to read the StudentDetailsType object
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if (sDetails != null) {
System.out.println("Server: " + formatStudentDetails(sDetails));
} else {
System.out.println("Server: Invalid Student Number\n");
}
}
public static String formatStudentDetails(StudentDetailsType s) {
StringBuilder b = new StringBuilder();
b.append("STUDENT NAME: " + s.getStudentName()+"\n");
b.append(String.format("\tMark1 = " + "%.2f\n", s.getResult1()));
b.append(String.format("\tMark2 = " + "%.2f\n", s.getResult2()));
b.append(String.format("\tMark3 = " + "%.2f\n\n", s.getResult3()));
return b.toString();
}
}
The Iterative Server code is composed of two classes StudentAdminServerIterative – main
server class and the StudentData class both in the same project. A JAR file of
StudentDetailsType is also available in the Libraries folder of this project.
import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.ServerSocket;
import java.net.Socket;
import java.io.ObjectOutputStream;
import studentdetailstype.StudentDetailsType;
import java.io.*;
public class StudentAdminServerIterative {
public static void main(String[] args) {
// determine if port to listen on is specified by user else use default
int portNumber = 4444; // default port number
if (args.length == 1) {
portNumber = Integer.parseInt(args[0]); // user specified port number
}
System.out.println("Student Server Started");
// create serverSocket to listen on
try (ServerSocket serverSocket = new ServerSocket(portNumber)) {
while (true) {
Socket clientSocket = serverSocket.accept();
try (BufferedReader is = new BufferedReader(new
InputStreamReader(clientSocket.getInputStream()));
ObjectOutputStream os = new ObjectOutputStream(new
BufferedOutputStream(clientSocket.getOutputStream()))) {
System.out.println("Client Accepted");
// send initial prompt to client
sendMessageToClient(os, "Server Saying Hello"); // send initial message to client
int num = parseToInt(is.readLine()); // read response from client and convert to integer
while (num != -1) {
// send studentDetails to client
sendMessageToClient(os, handleRequest(num));
num = parseToInt(is.readLine()); // read response from client and convert to integer
}
// send closing message to client
sendMessageToClient(os, "Server saying Goodby\n");
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} catch (IOException e) {
System.out.println("IOException:" + e.getMessage());
}
} // end while true
} catch (Exception e) {
System.out.println("Exception:" + e.getMessage());
} // end catch
} // end main
public static void sendMessageToClient(ObjectOutputStream os, Object msg) throws Exception {
os.writeObject(msg);
os.flush();
}
public static StudentDetailsType handleRequest(int studentNumber) {
StudentData studentData = new StudentData();
// read student number from client, then generate and send response
StudentDetailsType response = null;
if (new StudentData().validStudentNumberFlag(studentNumber)) {
response = studentData.getStudentDetails(studentNumber);
}
return response;
}
public static int parseToInt(String s) {
int studentNumber = 0;
try {
studentNumber = Integer.parseInt(s);
} catch (NumberFormatException e) {
System.out.println("Unable to read client command");
}
return studentNumber;
}
}
Typical interaction activity is as follows
Iterative Server running with one client connected and another trying to connect.
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(b) Multi-Threaded Server System has the same interaction with each client as
the Iterative server, however it can communicate with a number of clients
concurrently.
UML Diagram - Client and Multi-Threaded Server
The Multi-Threaded Server code is composed of two classes
StudentAdminServerMultiThreaded and StudentData both in the same project.
A JAR file of StudentDetailsType is also available in the Libraries folder of this project.
import java.net.*;
import java.io.*;
import studentdetailstype.StudentDetailsType;
public class StudentAdminServerMultiThreaded extends Thread {
/* This server acts as a multi-threaded "StudentAdminServerMultiThreaded" server.
* A number of clients can connect at once.
* It prompts for a Student Number
* from any connected client returns the appropriate student details.
*/
private final Socket clientSocket; // client socket for each thread connected
// Constructor
StudentAdminServerMultiThreaded(Socket clientSocket) {
this.clientSocket = clientSocket;
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} // end constructor
// run method for thread
@Override
public void run() {
try (BufferedReader is = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
ObjectOutputStream os = new ObjectOutputStream(new
BufferedOutputStream(clientSocket.getOutputStream()))) {
// send initial prompt to client
sendMessageToClient(os, "Server Saying Hello"); // send initial message to client
int num = parseToInt(is.readLine()); // read response from client and convert to integer
while (num != -1) {
// send studentDetails to client
sendMessageToClient(os, handleRequest(num));
num = parseToInt(is.readLine()); // read response from client and convert to integer
}
// send closing message to client
sendMessageToClient(os, "Server saying Goodby\n");
} catch (Exception e) {
System.out.println("IOException:" + e.getMessage());
}
} // end run
public static void main(String[] args) {
// determine if port to listen on is specified by user else use default
int portNumber = 4444; // default port number
if (args.length == 1) {
portNumber = Integer.parseInt(args[0]); // user specified port number
}
System.out.println("Student Server Started");
// create serverSocket to listen on
try (ServerSocket serverSocket = new ServerSocket(portNumber)) {
while (true) {
System.out.println("Multi Threaded Server Waiting");
Socket clientSocket = serverSocket.accept();
System.out.println("Client Accepted from " + clientSocket.getInetAddress());
// spawn a new thread to handle client
StudentAdminServerMultiThreaded studentAdminServerThread = new
StudentAdminServerMultiThreaded(clientSocket);
System.out.println("About to start new thread");
studentAdminServerThread.start();
} // end while true
} catch (Exception e) {
System.out.println("Exception:" + e.getMessage());
} // end catch
} // end main
public static void sendMessageToClient(ObjectOutputStream os, Object msg) throws Exception {
os.writeObject(msg);
os.flush();
}
public static StudentDetailsType handleRequest(int studentNumber) {
StudentData studentData = new StudentData();
// read student number from client, then generate and send response
StudentDetailsType response = null;
if (new StudentData().validStudentNumberFlag(studentNumber)) {
response = studentData.getStudentDetails(studentNumber);
}
return response;
}
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public static int parseToInt(String s) {
int studentNumber = 0;
try {
studentNumber = Integer.parseInt(s);
} catch (NumberFormatException e) {
System.out.println("Unable to read client command");
}
return studentNumber;
}
} // end StudentAdminServerMultiThreaded
Typical interaction activity is as follows
Multi-threaded Server running with two client connected and communicating.
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Solution 2
UML Diagram - Client and Multi-Threaded Server
The Multi-Threaded Server code (with database support) is composed of two classes
StudentAdminServerMultiThreadedDatabase and the StudentDataDB class, both in the
same project.
A JAR file of StudentDetailsType is also available in the Libraries folder of this project.
import java.net.*;
import java.io.*;
import studentdetailstype.StudentDetailsType;
public class StudentAdminServerMultiThreadedDatabase extends Thread {
/* This server acts as a multi-threaded "StudentAdminServerMultiThreadedDatabase" server.
* A number of clients can connect at once.
* It prompts for a Student Number
* from any connected client returns the appropriate student details.
*/
private final Socket clientSocket; // client socket for each thread connected
// Constructor
StudentAdminServerMultiThreadedDatabase(Socket clientSocket) {
this.clientSocket = clientSocket;
} // end constructor
// run method for thread
@Override
public void run() {
try (BufferedReader is = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
ObjectOutputStream os = new ObjectOutputStream(new
BufferedOutputStream(clientSocket.getOutputStream()))) {
// send initial prompt to client
sendMessageToClient(os, "Server Saying Hello"); // send initial message to client
int num = parseToInt(is.readLine()); // read response from client and convert to integer
while (num != -1) {
// send studentDetails to client
sendMessageToClient(os, handleRequest(num));
num = parseToInt(is.readLine()); // read response from client and convert to integer
}
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// send closing message to client
sendMessageToClient(os, "Server saying Goodby\n");
} catch (Exception e) {
System.out.println("IOException:" + e.getMessage());
}
} // end run
public static void main(String[] args) {
// determine if port to listen on is specified by user else use default
int portNumber = 4444; // default port number
if (args.length == 1) {
portNumber = Integer.parseInt(args[0]); // user specified port number
}
System.out.println("Student Server Started");
// create serverSocket to listen on
try (ServerSocket serverSocket = new ServerSocket(portNumber)) {
while (true) {
System.out.println("Multi Threaded Server Waiting (with database) ");
Socket clientSocket = serverSocket.accept();
System.out.println("Client Accepted from " + clientSocket.getInetAddress());
// spawn a new thread to handle client
StudentAdminServerMultiThreadedDatabase studentAdminServerThread = new
StudentAdminServerMultiThreadedDatabase(clientSocket);
System.out.println("About to start new thread");
studentAdminServerThread.start();
} // end while true
} catch (Exception e) {
System.out.println("Exception:" + e.getMessage());
} // end catch
} // end main
public static void sendMessageToClient(ObjectOutputStream os, Object msg) throws Exception {
os.writeObject(msg);
os.flush();
}
public static StudentDetailsType handleRequest(int studentNumber) {
StudentDataDB studentDataDB = new StudentDataDB();
// read student number from client, then generate and send response
StudentDetailsType response = null;
if (new StudentDataDB().validStudentNumberFlag(studentNumber)) {
response = studentDataDB.getStudentDetails(studentNumber);
}
return response;
}
public static int parseToInt(String s) {
int studentNumber = 0;
try {
studentNumber = Integer.parseInt(s);
} catch (NumberFormatException e) {
System.out.println("Unable to read client command");
}
return studentNumber;
}
} // end StudentAdminServerMultiThreadedDatabase
import java.sql.Connection;
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import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import studentdetailstype.StudentDetailsType;
public class StudentDataDB {
ResultSet rs;
public StudentDataDB() { //constructor
try {
String host = "jdbc:derby://localhost:1527/StudentDataDB";
String uName = "Tom";
String pWord = "MG121DTL";
Connection con = DriverManager.getConnection(host, uName, pWord);
Statement stmt = con.createStatement();
String SQL = "SELECT * FROM STUDENTDATA";
rs = stmt.executeQuery(SQL);
} catch (SQLException err) {
System.out.println(err.getMessage());
}
} // end constructor
public boolean validStudentNumberFlag(int studentNum) {
try {
while (rs.next()) {
if (studentNum == rs.getInt("STUDENTID")) {
return (true);
}
}
} catch (SQLException err) {
System.out.println(err.getMessage());
}
return (false);
} //end validStudentNumberFlag
public StudentDetailsType getStudentDetails(int studentNum) {
try {
while (rs.next()) {
if (studentNum == rs.getInt("STUDENTID")) {
// get the database details and create a StudentDetailsType object
String name = rs.getString("NAME");
float result1 = rs.getFloat("RESULT1");
float result2 = rs.getFloat("RESULT2");
float result3 = rs.getFloat("RESULT3");
return(new StudentDetailsType(studentNum, name, result1, result2, result3));
}
}
} catch (SQLException err) {
System.out.println(err.getMessage());
}
return null;
} //end getStudentDetails
} // end StudentDataDB
Typical interaction activity is as follows
Multi-threaded Server (with JavaDB database) running with two client connected and
communicating.
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Testing Invalid Input
Testing a Client Terminating
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END
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