Connection-oriented, concurrent server.

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.

Answer 1

Model the suites after Echo*3.java.
A static String, names, in the Thread class can be used for holding the names.
A synchronized method provides mutual protection to the names string.
```
class NameServerThread implements Runnable {
static String names;

MyStreamSocket myDataSocket;

NameServerThread(MyStreamSocket myDataSocket) {
this.myDataSocket = myDataSocket;
}

public void run( ) {
boolean done = false;
String newName;
try {
newName = myDataSocket.receiveMessage( );
updateNames(newName);

// Now send the names to the requestor
myDataSocket.sendMessage(names);
myDataSocket.close( );
}// end try
catch (Exception ex) {
System.out.println("Exception caught in thread: " + ex);
}
} //end run

private synchronized void updateNames(String newName ){
names += newName + "\n";
} //end updateNames

} //end class
```