时间：2018-12-01

概述：聊天室 服务器 客户端

在网络上经常进各种聊天室，本例通过编程实现了C/S 模式的聊天室服务器和客户端。实现方法：ChatServer 类实现了一个聊天室服务器端， 此类有一个构造器， 在构造器中使用newServerSocket()建立一个Socket 连接。RunServer()方法中运行聊天服务，通过Socket 类的getInetAddress().getHostName() 方法获得主机名， 建立新的ChatHandler 对象实例， 在synchronized (clients)中取得与客户端的同步。内部类ChatHandler 继承了Thread 类，在此线程run()方法中处理一次交谈。Close()方法关闭与客户端的连接。ChatRoom 类继承了Applet，在init()中通过new Frame()创建聊天窗体，并在此窗体中设置窗体布局。在login()方法中，通过new Socket(serverHost, port)建立与服务器的连接，通过new Thread()产生新的聊天线程。在logout()方法中，使用sock.close()关闭连接。程序代码：

1．编写Chat 类的基本框架，该类定义了从客户端到服务器的信息的第一个字节常量，该类还包括返回值为布尔型的isValidLoginName()方法，该方法用于判断登录名是否合法，代码如下：

public class Chat

{

public static final int PORTNUM = 9999;

public static final int MAX_LOGIN_LENGTH = 20;

public static final char SEPARATOR = '\\';

public static final char COMMAND = '\\';

public static final char CMD_LOGIN = 'L';

public static final char CMD_QUIT = 'Q';

public static final char CMD_MESG = 'M';

public static final char CMD_BCAST = 'B';

public static final char RESP_PUBLIC = 'P';

public static final char RESP_PRIVATE = 'M';

public static final char RESP_SYSTEM = 'S';

public static boolean isValidLoginName(String login)

{

if (login.length() > MAX_LOGIN_LENGTH)

return false;

return true;

}

}

2．编写ChatServer 类基本框架，该类为聊天室服务器程序。该类包括如下字段：字符串常量CHATMASTER_ID 和SEP，ServerSocket 对象变量servSock，ArrayList 对象变量clients，布尔型变量DEBUG。该类包括main()方法、构造器方法、runServer()方法、log()方法，该类还包括一个内部类ChatHandler，代码如下：

public class ChatServer

{

protected final static String CHATMASTER_ID = "ChatMaster";

protected final static String SEP = ": ";

protected ServerSocket servSock;

protected ArrayList clients;

private static boolean DEBUG = false;

//方法

public static void main(String[] argv);

ChatServer();

public void runServer();

protected void log(String s);

protected class ChatHandler extends Thread;

}

3．Main()方法用于构建一个ChatServer 类实例，运行服务器程序，代码如下：

public static void main(String[] argv)

{

System.out.println("Chat Server 0.1 starting...");

if (argv.length == 1 && argv[0].equals("-debug"))

DEBUG = true;

ChatServer w = new ChatServer();

w.runServer();

System.out.println("**ERROR* Chat Server 0.1 quitting");

}

4．ChatServer 的构造器用于构建该类实例，代码如下：

ChatServer()

{

clients = new ArrayList();

try

{

servSock = new ServerSocket(Chat.PORTNUM);

System.out.println("Chat Server Listening on port " + Chat.PORTNUM);

}

catch(IOException e)

{

log("IO Exception in ChatServer.");

System.exit(0);

}

}

5．RunServer()方法用于运行服务器程序：

public void runServer() {

try

{

while (true)

{

Socket us = servSock.accept();

String hostName = us.getInetAddress().getHostName();

System.out.println("Accepted from " + hostName);

ChatHandler cl = new ChatHandler(us, hostName);

synchronized (clients) {

clients.add(cl);

cl.start();

if (clients.size() == 1)

cl.send(CHATMASTER_ID, "Welcome! you're the first one here");

else {

cl.send(CHATMASTER_ID, "Welcome! you're the latest of " +clients.size() + " users.");

}

}

}

} catch(IOException e) {

log("IO Exception in runServer: " + e);

System.exit(0);

}

}

6．Log()方法用于输出字符串，代码如下：

protected void log(String s)

{

System.out.println(s);

}

7．编写内部类ChatHandler 的基本框架，该类用于处理每个交谈信息，该类继承了Thread 类，包括如下字段：Socket 对象变量clientSock，BufferedReader 对象变量is，PrintWriter 对象变量pw，字符串变量clientIP 和login，该类还包括构造器方法、run()方法、close()方法、send()方法、psend()方法、broadcast()方法、lookup()方法、toString()方法，代码如下：

protected class ChatHandler extends Thread {

protected Socket clientSock;

protected BufferedReader is;

protected PrintWriter pw;

protected String clientIP;

protected String login;

public ChatHandler(Socket sock, String clnt) throws IOException;

public void run();

protected void close();

public void send(String sender, String mesg);

protected void psend(String sender, String msg);

public void broadcast(String sender, String mesg);

protected ChatHandler lookup(String nick);

public String toString();

}

8．ChatHandler 构造器用于构建该类实例，代码如下：

public ChatHandler(Socket sock, String clnt) throws IOException

{

clientSock = sock;

clientIP = clnt;

is = new BufferedReader( new InputStreamReader(sock.getInputStream()));

pw = new PrintWriter(sock.getOutputStream(), true);

}

9．run()方法用于用于处理每一次交谈：

public void run()

{

String line;

try {

while ((line = is.readLine()) != null) {

char c = line.charAt(0);

line = line.substring(1);

switch (c) {

case Chat.CMD_LOGIN:

if (!Chat.isValidLoginName(line)) {

send(CHATMASTER_ID, "LOGIN " + line + " invalid");

log("LOGIN INVALID from " + clientIP);

continue;

}

login = line;

broadcast(CHATMASTER_ID, login + " joins us, for a total of " +clients.size() + " users");

break;

case Chat.CMD_MESG:

if (login == null) {

send(CHATMASTER_ID, "please login first");

continue;

}

int where = line.indexOf(Chat.SEPARATOR);

String recip = line.substring(0, where);

String mesg = line.substring(where+1);

log("MESG: " + login + "-->" + recip + ": "+ mesg);

ChatHandler cl = lookup(recip);

if (cl == null)

psend(CHATMASTER_ID, recip + " not logged in.");

else

cl.psend(login, mesg);

break;

case Chat.CMD_QUIT:

broadcast(CHATMASTER_ID, "Goodbye to " + login + "@" + clientIP);

close();

return;

case Chat.CMD_BCAST:

if (login != null)

broadcast(login, line);

else

log("B

break;

default:

log("Unknown cmd " + c + " from " + login + "@" + clientIP);

}

}

} catch (IOException e) {

log("IO Exception: " + e);

} finally {

System.out.println(login + SEP + "All Done");

synchronized(clients) {

clients.remove(this);

if (clients.size() == 0) {

System.out.println(CHATMASTER_ID + SEP +"Im so lonely I could cry...");

} else if (clients.size() == 1) {

ChatHandler last = (ChatHandler)clients.get(0);

last.send(CHATMASTER_ID,"Hey, you're talking to yourself again");

} else {

broadcast(CHATMASTER_ID,"There are now " + clients.size() + " users");

}

}

}

}

10．close()方法用于关闭服务器：

protected void close() {

if (clientSock == null) {

log("close when not open");

return;

}

try {

clientSock.close();

clientSock = null;

} catch (IOException e) {

log("Failure during close to " + clientIP);

}

}

11．Send()方法用于发送一条信息给用户，代码如下：

public void send(String sender, String mesg)

{

pw.println(sender + SEP + mesg);

}

12．Psend()方法用于发送一条私有信息给用户：

protected void psend(String sender, String msg)

{

send("", msg);

}

13．Broadcast()方法用于发送一条信息给所有用户：

public void broadcast(String sender, String mesg)

{

System.out.println("Broadcasting " + sender + SEP + mesg);

for (int i=0; i

ChatHandler sib = (ChatHandler)clients.get(i);

if (DEBUG)

System.out.println("Sending to " + sib);

sib.send(sender, mesg);

}

if (DEBUG) System.out.println("Done broadcast");

}

14．Lookup()方法用于与客户端同步：

protected ChatHandler lookup(String nick)

{

synchronized(clients) {

for (int i=0; i

ChatHandler cl = (ChatHandler)clients.get(i);

if (cl.login.equals(nick))

return cl;

}

}

return null;

}

15．toString()方法用于将ChatHandler 作为字符串返回：

public String toString()

{

return "ChatHandler[" + login + "]";

}

16．ChatServer 类应该引入如下包：

import java.io.*;

import java.net.*;

import java.util.*;