Create one or more of the following suites for the protocol:

Question

Using the three-tier software architecture presented in this chapter, design and implement a client-server suite for the following protocol (it is not a well-known service): Each client sends to the server a name. The server accumulates the names received from successive clients (by appending each, with a linefeed (‘
’), to a static string). Upon receiving a name, the server sends the names that it has collected to the client. The figure below illustrates the sequence diagram of a session of the protocol.





i.

Connectionless server;

Answer 1

Model the suite after the Echo*1 suite. The difference is that in the Client module, the ClientHelper’s method is invoked to send a single string containing a name to the server, receives a string back, display the string received, then exit.
```
public class NameClient1 {
public static void main(String[] args) {
InputStreamReader is = new InputStreamReader(System.in);
BufferedReader br = new BufferedReader(is);
try {
System.out.println("Welcome to the Name client.\n" +
"What is the name of the server host?");
String hostName = br.readLine();
if (hostName.length() == 0) // if user did not enter a name
hostName = "localhost"; // use the default host name
System.out.println("What is the port number of the server host?");
String portNum = br.readLine();
if (portNum.length() == 0)
portNum = "1234"; // default port number
EchoClientHelper1 helper =
new EchoClientHelper1(hostName, portNum);
boolean done = false;
String message, names;
System.out.println("Enter a name");
message = br.readLine( );
names = helper.getNames( message);
System.out.println(name);
} // end try
catch (Exception ex) {
ex.printStackTrace( );
}
} //end main
} // end class
```

The server must maintain a string for accumulating the names. The service logic requires no change. The server class looks like this:
```
public class NameServer1 {
public static void main(String[] args) {
String names = ""; // string for accumulating the names
int serverPort = 1234; // default port
if (args.length == 1 )
serverPort = Integer.parseInt(args[0]);
try {
// instantiates a datagram socket for both sending
// and receiving data
MyServerDatagramSocket mySocket = new
MyServerDatagramSocket(serverPort);
System.out.println("Name server ready.");
while (true) { // forever loop
DatagramMessage request =
mySocket.receiveMessageAndSender();
System.out.println("Request received");
String message = (request.getMessage( )).trim( );
System.out.println("name received: "+ message);
names += message + "\n";
// Now send the names back to the requestor
mySocket.sendMessage(request.getAddress( ),
request.getPort( ), names);
} //end while
} // end try
…
```