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The Tutorial Questions and Lab Projects of Week 2
Tutorial Questions
1. A server creates a port which it uses to receive requests from clients. Discuss the design
issues concerning the relationship between the name of this port and the names used by
clients.
2. Sun XDR marshals data by converting it into a standard big-endian form before transmission.
Discuss the advantages and disadvantages of this method when compared with CORBA’s
CDR.
3. Why is there no explicit data-typing in CORBA CDR?
4. Write an algorithm in pseudocode to describe the serialization procedure. The algorithm
should show when handles are defined or substituted for classes and instances. Describe the
serialized form that your algorithm would produce when serializing an instance of the
following class Couple.
class Couple implements Serializable{
private Person one;
private Person two;
public Couple(Person a, Person b) {
one = a;
two = b;
}
}
5. Outline how connectionless communication between a client and a server is established and
proceeded by using sockets.
Lab Projects
On the lecture slides of Week 2, there is client/server example using UDP protocol. This example
consists of programs: UDPClient.java and UDPserver.java.
Task 1:
1. Revise the two programs so that the outputs of the programs like the following screenshots.
2. Compile the two programs to generate Java class files: UDPClient.class and
UPDServer.class.
3. Run the two java classes on two JVMs (Java Virtual Machines) on a single physical machine
and check the program outputs.
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Task2:
From the outputs of UDPClient or UDPServer, you have seen that there are many blank lines for
each request or response.
1. Investigate why there are blank lines in the outputs.
2. Revise the two programs: UDPCLient.java and UDPserver.java so that the programs
just output the strings of the request or the response but remove the blank lines. The
outputs of the revised programs should like those from UDPCLient1 and UDPserver1 as in
the following screenshots.
3. Compile the revised programs, run them and check the outputs.
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Note:
To make the above revision, you need to investigate Java APIs at least for the class: String and
DatagramPacket. The reference is the Java APIs document from Sun Microsystems. It is online at:
http://docs.oracle.com/javase/6/docs/api/
Task 3:
Define a Book class, which has the fields: Title, Author, Publisher, PublishYear and ISBN.
The class should have methods for getting value from and setting value onto each field.
Write a program to create two objects from the Book class and save the objects into a file onto
permanent storage by using Java serialization.
The following are the screenshots of the output of such a program and the file that stores the Book
objects.
http://docs.oracle.com/javase/6/docs/api/�
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Task 4:
Write another program to read the file from the hard drive and restore the two objects of Book.
After that, print the publishing information for each book to confirm the serialization and
deserialization are successful.
The following is the screenshot of the outputs of such a program.
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The reference resources for this project are:
1. Week 2 lecture slides
2. Java object serialization specification from Sun Microsystems at:
http://docs.oracle.com/javase/1.3/docs/guide/serialization/
3. Java IO APIs on FileOutputStream, ObjectOutputStream, FileInputStream, and
ObjectInputStream.
http://docs.oracle.com/javase/6/docs/api/
http://docs.oracle.com/javase/1.3/docs/guide/serialization/�
http://docs.oracle.com/javase/6/docs/api/�