BSc ( Hons) Computer Science with Network Security. Examinations for / Semester 2

Transcription

1 BSc ( Hons) Computer Science with Network Security Cohort: BCNS/16B/FT Examinations for / Semester 2 Resit Examinations for BCNS/15B/FT & BCNS/16A/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 5 pages. Page 1 of 5

2 ANSWER ALL QUESTIONS QUESTION 1: (35 MARKS) (a) Write a program that will count the number of lines in each file that is specified on the command line. Assume that the files are text files. Note that multiple files can be specified, as in: java LineCounts file1.txt file2.txt file3.txt Write each file name, along with the number of lines in that file, to standard output. If an error occurs while trying to read from one of the files, you should print an error message for that file, but you should still process all the remaining files. (15 marks) (b) Examine the below codes : dfdstring[] supported = server.getsupportedciphersuites(); String[] anonciphersuitessupported = new String[supported.length]; int numanonciphersuitessupported = 0; for (int i = 0; i < supported.length; i++) { if (supported[i].indexof("_anon_") > 0) { anonciphersuitessupported[numanonciphersuitessupported++] = supported[i]; String[] oldenabled = server.getenabledciphersuites(); String[] newenabled = new String[oldEnabled.length + numanonciphersuitessupported]; System.arraycopy(oldEnabled, 0, newenabled, 0, oldenabled.length); System.arraycopy(anonCipherSuitesSupported, 0, newenabled, oldenabled.length, numanonciphersuitessupported); server.setenabledciphersuites(newenabled); You are required to briefly describe the logic in the above piece of code? Page 2 of 5

3 (c) In Java, input/output is done using streams. Streams are an abstraction. Explain what this means and why it is important? (d) In The package java.io includes a class named URL. What does an object of type URL represent, and how is it used? (3 marks) (e) What are the differences between URI, URN and URL? QUESTION 2: (25 MARKS) (a) You are the new network administrator of XYZ company, you have been assigned the ip address /28. i) What is the subnet mask of this ip address? ii) Calculate the number of hosts you can configure in your network? (b) In the transport header of a packet you have the source port and the destination port. Why the receiver needs to know the destination port and what is the source port used for? (c) Write a serversocket program name myserver.java that will listen on port 6789 and read a line of text from the client, convert it to uppercase and send it back to the client. Below are the characteristics or steps used to write such program: i) Have an exception handler for the main method ii) Constructs a ServerSocket object to listen on port 6789 iii) Infinite loop to continually process the request. Page 3 of 5

4 iv) wait for a connection to be made to the ServerSocket. Once connected, the connsock socket can be used to communicate with the client. v) Construct a BufferedReader to read text data line-by-line from the client vi) Construct an OutputDataStream to send data to the client vii) Read a line of text from the client, convert it to upper case and send it back to the client. (15 marks) QUESTION 3: (40 MARKS) (a) What is the function of a thread scheduler? (2 marks) (b) Network server programs are often multithreaded. Explain what this means and why it is true? (c) What is the expected output of the following piece of codes : public class TestInterruptingThread4 extends Thread{ public void run(){ for(int i=3;i<=4;i++){ if(thread.interrupted()){ System.out.println("code for interrupted thread"); else{ System.out.println("code for normal thread"); //end of for loop public static void main(string args[]){ TestInterruptingThread4 t1=new TestInterruptingThread4(); TestInterruptingThread4 t2=new TestInterruptingThread4(); t1.start(); t1.interrupt(); t2.start(); Page 4 of 5

5 (d) Write an IntSleep application that creates a background thread to repeatedly output Hello and then sleep for 100 milliseconds. After sleeping for 2 seconds the default main thread should interrupt the background thread, which should break out of the loop after outputting interrupted. (e) Explain the need of synchronization in a multithreaded programs? (4 marks) (f) In non blocking IO, explain why buffers and channel are used? (g) Describe the following Java classes in RMI : java.rmiserver.unicastremoteobject java.rmi.naming java.rmi.remoteexception java.rmi.remote java.rmi.notboundexception (10 marks) ***END OF QUESTION PAPER*** Page 5 of 5