Java在Client/Server中應用(2)

三. 編寫服務器類Java程序

// Server.Java  
    import Java.io.*;  
    import Java.Net.*;  
    public class Server extends Thread  
    {  
    public final static int Default_Port=6543;  
    protectd int port;  
    protectd ServerSockt listen_socket;  
    // 定義出錯例程：如果出現異常錯誤，退出程序。  
    Public static void fail(Exception e, String msg)  
    {  
    System.err.println(msg + ": " + e);  
    System.exit(1);  
    }  
    // 定義並啟動服務器的Socket 例程，監聽客戶機的連接請求。  
    public Server(int port)  
    {  
    if(port == 0) port = Default_Port;  
    this.port = port;  
    try 
    {  
    listen_socket = new ServerSocket(port);  
    }  
    catch(IOException e) fail(e, "Exception creating server socket");  
    System.out.println("Server: listening on port" + port);  
    This.start();  
    }  
/* 下面為服務器監聽線程的主程序。該線程一直循環執行，監聽並接受客戶機發出的連接請求。對每一個連接，均產生一個連接對象與之對應，通過Socket 通道進行通信。*/ 
    public void run()  
    {  
    try 
    {  
    while(true)  
    {  
    Socket clIEnt_socket = listen_socket.accept();  
    Connection c = new Connection(clIEnt_socket);  
    }  
    }  
    catch(IOException e) fail(e,"Exception while listening for connections")  
    }  
    // 啟動服務器主程序  
    public static void main(String args[])  
    {  
    int port = 0;  
    if (args.length == 1)  
    {  
    try port = Integer.parseInt(args[0]);  
    catch(NumberFormatException e) port = 0;  
    }  
    new Server(port);  
    // End of the main  
    } // End of Server class  
    //以下定義了Connection 類，它是用來處理與客戶機的所有通信的線程。  
    class Connection extends Thread  
    {  
    protected Socket clIEnt;  
    protected DataInputStream in;  
    protected PrintStream out;  
    // 初始化通信流並啟動線程  
    public Connection(Socket clIEnt_socket)  
    {  
    client = clIEnt_socket;  
    try 
    {  
    in = new DataInputStream(clIEnt.getinputStream());  
    out = new PrintStream(clIEnt.getOutputStream());  
    }  
    catch(IOException e)  
    {  
    try clIEnt.close();  
    catch(IOException e2);  
    System.err.println("Exception while getting socket streram: " + e);  
    Return;  
    }  
    this.start;  
    } // End of Connection method  
    // 服務例程：讀出一行文本；反轉文本；返回文本。  
    public void run()  
    {  
    String line;  
    StringBuffer revline;  
    int len;  
    try 
    {  
    for(;;)  
    {  
    // Read a line  
    line = in.readline();  
    if(line == null) break;  
    // Reverse the line  
    len = line.length();  
    revline = new StringBuffer(len);  
    for(int i = len-1; i >=0; i--)  
    revline.insert(len-1-I;line.charAt(i));  
    // Write out the reverse line  
    out.println(revline);  
    }  
    catch(IOException e);  
    finally try clIEnt.close();  
    catch(IOException e2);  
    }  
    // End of run method  
    }  
    // End of Connection class 

四. 編寫客戶機類Java 程序

// ClIEnt.Java  
    import Java.io.*;  
    import Java.Net.*;  
    public class ClIEnt extends 
    {  
    public static final int Default_Port = 6543;  
    // 定義出錯例程  
    public static final void usage()  
    {  
    System.out.println("Usage: Java ClIEnt []");  
    System.exit(0);  
    }  
    public static void main(String args[])  
    {  
    int port = Default_Port;  
    Socket s = null;  
    // 解析端口參數  
    if ((args.length != 1)&&(args.length != 2 )) usage();  
    if (args.length == 1)  
    port = Default_Port;  
    else 
    {  
    try port = Integer.parseInt(args[1]);  
    catch(NumberFormaatException e) usage();  
    }  
    try{  
    // 產生一個Socket ，通過指定的端口與主機通信。  
    s = new Socket(args[0], port);  
    // 產生用於發出和接收的文本字符流  
    DataInputStream sin = new DataInputStream(s.getInputStream());  
    PrintStream sout = new DataInputStream(s.getInputStream());  
    // 從控制台讀入字符流  
    DataInputStream in = new DataInputStream(System.in);  
    // 返回連接的地址和端口  
    ystem.out.println("Connected to"+s.getInetAddress()+":"+ s.getPort());  
    String line;  
    For(;;)  
    {  
    // 顯示提示符  
    System.out.print(" >");  
    System.out.flush();  
    // 讀入控制台輸入的一行字符  
    line = in.readline();  
    if (line == null) break;  
    // 將接收的文本行送至服務器  
    sout.println(line);  
    // 從服務器接收一行字符  
    line = sin.readline();  
    // Check if connection is closed(i.e. for EOF)  
    if(line == null)  
    {  
    System.out.println("Connection closed by server.");  
    Break;  
    }  
    // 在控制台上顯示接收的字符  
    System.out.println(line);  
    }  
    // End of for loop  
    }  
    // End of try  
    catch(IOException e ) System.err.println(e);  
    // Always be sure to close the socket  
    finally 
    {  
    try if(s != null) s.close();  
    catch(IOException e2);  
    }  
    } // End of main  
    } // End of ClIEnt  

運行該客戶機程序時，必須以服務器主機名作為第一個參數，服務器端口號為第二個參數，其中服務器端口號可缺省。