Java How to Program Fourth Edition - DCC

998 Networking Chapter 17
Method sendData sends the String object to the client, flushes the output buffer and
appends the same String to the JTextArea in the server window.
Notice that the Server receives a connection, processes the connection, closes the
connection and waits for the next connection. A more likely scenario would be a Server
that receives a connection, sets up that connection to be processed as a separate thread of
execution, and waits for new connections. The separate threads that process existing connections
can continue to execute while the Server concentrates on new connection
requests.
Like class Server, class Client’s (Fig. 17.5) constructor creates the GUI of the
application (a JTextField and a JTextArea). The Client object displays its output
in a JTextArea. When the main method (line 175–188) executes, it creates an instance
of class Client, specifies the window’s default close operation and calls method run-
Client (defined at lines 63–90). In this example, you can execute the client from any
computer on the Internet and specify the Internet address or host name of the server computer
as a command-line argument to the program. For example,
java Client 192.168.1.15
connects to the Server on the computer with Internet address 192.168.1.15.
1 // Fig. 17.5: Client.java
2 // Set up a Client that will read information sent
3 // from a Server and display the information.
4
5 // Java core packages
6 import java.io.*;
7 import java.net.*;
8 import java.awt.*;
9 import java.awt.event.*;
10
11 // Java extension packages
12 import javax.swing.*;
13
14 public class Client extends JFrame {
15 private JTextField enterField;
16 private JTextArea displayArea;
17 private ObjectOutputStream output;
18 private ObjectInputStream input;
19 private String message = "";
20 private String chatServer;
21 private Socket client;
22
23 // initialize chatServer and set up GUI
24 public Client( String host )
25 {
26 super( "Client" );
27
28 // set server to which this client connects
29 chatServer = host;
Fig. Fig. 17.5 17.5 Demonstrating the client portion of a stream-socket connection between a
client and a server (part 1 of 5).