BSc (Hons) Computer Science with Network Security. Examinations for 2017 / Semester 2. Resit Examinations for BCNS/15A/FT

Transcription

1 BSc (Hons) Computer Science with Network Security Cohort: BCNS/16A/FT Examinations for 2017 / Semester 2 Resit Examinations for BCNS/15A/FT MODULE: NETWORK PROGRAMMING MODULE CODE: CAN2113C Duration: 3 Hours Instructions to Candidates: 1. Answer all questions. 2. Questions may be answered in any order but your answers but show the question number clearly. 3. Always start a new question on a fresh page. 4. All sample codes will need to be in Java Programming Language. 5. Total marks 100. This question paper contains 3 questions and 7 pages. Page 1 of 7

2 ANSWER ALL QUESTIONS QUESTION 1: (35 MARKS) (a) Streams can be divided into character based and byte based. Can you mention three subclasses of Byte based stream and two subclasses of Character based stream? (b) Make use of three classes you mentioned above to demonstrate how you would move data from a source to a destination? (c) In java programming, concurrent programming is mostly concerned with threads. By making use of a diagram show the different states of a thread? (10 marks) (d) By using an example, explain the situation of deadlock in java threads. Provide two ways to prevent such situation to happen? (e) There is a class name SimpleThreads that make use of different methods in thread. You are required to comment on each line of code hereby clearly explaining the different thread methods and finally give its expected output when it is run? Page 2 of 7

3 public class SimpleThreads { static void threadmessage(string message) { String threadname = Thread.currentThread().getName(); System.out.format("%s: %s%n", threadname, message); private static class MessageLoop implements Runnable { public void run() { String importantinfo[] = { "Mares eat oats", "Does eat oats", "Little lambs eat ivy", "A kid will eat ivy too" ; try { for (int i = 0; i < importantinfo.length; i++) { Thread.sleep(4000);. threadmessage(importantinfo[i]); catch (InterruptedException e) { threadmessage("i wasn't done!"); ( 10 marks) Page 3 of 7

4 QUESTION 2: (25 MARKS) (a) As a freshly graduated java network programmer, you have been asked to explain briefly the following concept : i) Ip address ii) subnet mask iii) DNS iv) URL v) Socket (b) Java has a class named java.net.inetaddress which is a high level representation of an IP address. Explain the three main purposes of this class. (3 marks) (c) Write a small program in java that will find out the ip address and name of the machine on which it is running? (d) Examine the below lines of codes : Page 4 of 7

5 for (int i = 0; i < args.length; i++) { try { URL u = new URL(args[i]); System.out.println("The URL is " + u); System.out.println("The scheme is " + u.getprotocol()); System.out.println("The user info is " + u.getuserinfo()); String host = u.gethost(); if (host!= null) { int atsign = host.indexof('@'); if (atsign!= -1) host = host.substring(atsign+1); System.out.println("The host is " + host); else { System.out.println("The host is null."); System.out.println("The port is " + u.getport()); System.out.println("The path is " + u.getpath()); System.out.println("The ref is " + u.getref()); System.out.println("The query string is " + u.getquery()); catch (MalformedURLException ex) { System.err.println(args[i] + " is not a URL I understand."); System.out.println(); What will be the expected output when running the above code against the three URL below? 1.) ftp://mp3:mp3@ :21000/c%3a/ \ 2.) 3.) (12 marks) Page 5 of 7

6 QUESTION 3: (40 MARKS) (a) Describe the seven basic operations of a socket. (7 marks) (b) You are required to write a server program named DatagramSender that will send datagrams to a host named "server.com" on the udp port 181. Below are the steps required to implement the DatagramSender program: Create a new DatagramPacket Put some data which constitutes your message in the new DatagramPacket Set a destination address and port so that the network knows where to deliver the datagram ( host server.com and port 181 ) Create a socket with a dynamically allocated port number Send the packet through the socket onto the network Similarly you will need to write the program DatagramReceiver with the following steps : Create an empty DatagramPacket (and allocate a buffer for the incoming data) Create a DatagramSocket on an agreed socket number to provide access to arrivals Use the socket to receive the datagram (the thread will block until a new datagram arrives) Extract the data bytes which make up the message (18 marks) Page 6 of 7

7 (c) Multiple clients are quite often connected to a single server at the same time. Typically a server runs constantly on a server computer, and clients from all over the internet may want to connect to it. Write a piece of code to explain how the server will handle the multiple clients connections simultaneously (d) Use your knowledge in the field of distributed object applications in Java to define RMI applications and explain the diagram below : (10 marks) ***END OF QUESTION PAPER*** Page 7 of 7