Java NIO示例：多人网络聊天室
一个多客户端聊天室，支持多客户端聊天，有如下功能：
- 功能1： 客户端通过Java NIO连接到服务端，支持多客户端的连接
- 功能2：客户端初次连接时，服务端提示输入昵称，如果昵称已经有人使用，提示重新输入，如果昵称唯一，则登录成功，之后发送消息都需要按照规定格式带着昵称发送消息
- 功能3：客户端登录后，发送已经设置好的欢迎信息和在线人数给客户端，并且通知其他客户端该客户端上线
- 功能4：服务器收到已登录客户端输入内容，转发至其他登录客户端。
- 功能5 TODO：客户端下线检测 方案是：客户端在线的时候发送心跳，服务端用TimeCacheMap自动删除过期对象，同时通知线上用户删掉的用户下线。
下面演示下效果，代码见附录！
启动服务器，监听某个端口
服务器console
Server is listening now...
启动一个客户端，连接服务器
服务器console
Server is listening now...
Server is listening from client :/127.0.0.1:50206
客户端console
Please input your name.
客户端输入一个昵称
服务端console
Server is listening now...
Server is listening from client :/127.0.0.1:50206
Server is listening from client /127.0.0.1:50206 data rev is: byr1#@#
客户端console
Please input your name.
byr1
welcome byr1 to chat room! Online numbers:1
再启动另外一个客户端，并输入昵称
服务端console
Server is listening now...
Server is listening from client :/127.0.0.1:50206
Server is listening from client /127.0.0.1:50206 data rev is: byr1#@#
Server is listening from client :/127.0.0.1:50261
Server is listening from client /127.0.0.1:50261 data rev is: byr2#@#
客户端byr1 console
Please input your name.
byr1
welcome byr1 to chat room! Online numbers:1
welcome byr2 to chat room! Online numbers:2
客户端byr2 console
Please input your name.
byr2
welcome byr2 to chat room! Online numbers:2
客户端byr1发送一个消息，客户byr2回一条消息
服务端console
Server is listening now...
Server is listening from client :/127.0.0.1:50206
Server is listening from client /127.0.0.1:50206 data rev is: byr1#@#
Server is listening from client :/127.0.0.1:50261
Server is listening from client /127.0.0.1:50261 data rev is: byr2#@#
Server is listening from client /127.0.0.1:50206 data rev is: byr1#@#hello byr2, a nice day, isn't it?
Server is listening from client /127.0.0.1:50261 data rev is: byr2#@#fine
客户端byr1 console
Please input your name.
byr1
welcome byr1 to chat room! Online numbers:1
welcome byr2 to chat room! Online numbers:2
hello byr2, a nice day, isn't it?
byr2 say fine
客户端byr2 console
Please input your name.
byr2
welcome byr2 to chat room! Online numbers:2
byr1 say hello byr2, a nice day, isn't it?
fine
附录：server和client代码
server代码
package com.huahuiyang.channel;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.Channel;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.nio.charset.Charset;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;
/**
* 网络多客户端聊天室
* 功能1： 客户端通过Java NIO连接到服务端，支持多客户端的连接
* 功能2：客户端初次连接时，服务端提示输入昵称，如果昵称已经有人使用，提示重新输入，如果昵称唯一，则登录成功，之后发送消息都需要按照规定格式带着昵称发送消息
* 功能3：客户端登录后，发送已经设置好的欢迎信息和在线人数给客户端，并且通知其他客户端该客户端上线
* 功能4：服务器收到已登录客户端输入内容，转发至其他登录客户端。
*
* TODO 客户端下线检测
*/
public class ChatRoomServer {
private Selector selector = null;
static final int port = 9999;
private Charset charset = Charset.forName("UTF-8");
//用来记录在线人数，以及昵称
private static HashSet<String> users = new HashSet<String>();
private static String USER_EXIST = "system message: user exist, please change a name";
//相当于自定义协议格式，与客户端协商好
private static String USER_CONTENT_SPILIT = "#@#";
private static boolean flag = false;
public void init() throws IOException
{
selector = Selector.open();
ServerSocketChannel server = ServerSocketChannel.open();
server.bind(new InetSocketAddress(port));
//非阻塞的方式
server.configureBlocking(false);
//注册到选择器上，设置为监听状态
server.register(selector, SelectionKey.OP_ACCEPT);
System.out.println("Server is listening now...");
while(true) {
int readyChannels = selector.select();
if(readyChannels == 0) continue;
Set selectedKeys = selector.selectedKeys(); //可以通过这个方法，知道可用通道的集合
Iterator keyIterator = selectedKeys.iterator();
while(keyIterator.hasNext()) {
SelectionKey sk = (SelectionKey) keyIterator.next();
keyIterator.remove();
dealWithSelectionKey(server,sk);
}
}
}
public void dealWithSelectionKey(ServerSocketChannel server,SelectionKey sk) throws IOException {
if(sk.isAcceptable())
{
SocketChannel sc = server.accept();
//非阻塞模式
sc.configureBlocking(false);
//注册选择器，并设置为读取模式，收到一个连接请求，然后起一个SocketChannel，并注册到selector上，之后这个连接的数据，就由这个SocketChannel处理
sc.register(selector, SelectionKey.OP_READ);
//将此对应的channel设置为准备接受其他客户端请求
sk.interestOps(SelectionKey.OP_ACCEPT);
System.out.println("Server is listening from client :" + sc.getRemoteAddress());
sc.write(charset.encode("Please input your name."));
}
//处理来自客户端的数据读取请求
if(sk.isReadable())
{
//返回该SelectionKey对应的 Channel，其中有数据需要读取
SocketChannel sc = (SocketChannel)sk.channel();
ByteBuffer buff = ByteBuffer.allocate(1024);
StringBuilder content = new StringBuilder();
try
{
while(sc.read(buff) > 0)
{
buff.flip();
content.append(charset.decode(buff));
}
System.out.println("Server is listening from client " + sc.getRemoteAddress() + " data rev is: " + content);
//将此对应的channel设置为准备下一次接受数据
sk.interestOps(SelectionKey.OP_READ);
}
catch (IOException io)
{
sk.cancel();
if(sk.channel() != null)
{
sk.channel().close();
}
}
if(content.length() > 0)
{
String[] arrayContent = content.toString().split(USER_CONTENT_SPILIT);
//注册用户
if(arrayContent != null && arrayContent.length ==1) {
String name = arrayContent[0];
if(users.contains(name)) {
sc.write(charset.encode(USER_EXIST));
} else {
users.add(name);
int num = OnlineNum(selector);
String message = "welcome "+name+" to chat room! Online numbers:"+num;
BroadCast(selector, null, message);
}
}
//注册完了，发送消息
else if(arrayContent != null && arrayContent.length >1){
String name = arrayContent[0];
String message = content.substring(name.length()+USER_CONTENT_SPILIT.length());
message = name + " say " + message;
if(users.contains(name)) {
//不回发给发送此内容的客户端
BroadCast(selector, sc, message);
}
}
}
}
}
//TODO 要是能检测下线，就不用这么统计了
public static int OnlineNum(Selector selector) {
int res = 0;
for(SelectionKey key : selector.keys())
{
Channel targetchannel = key.channel();
if(targetchannel instanceof SocketChannel)
{
res++;
}
}
return res;
}
public void BroadCast(Selector selector, SocketChannel except, String content) throws IOException {
//广播数据到所有的SocketChannel中
for(SelectionKey key : selector.keys())
{
Channel targetchannel = key.channel();
//如果except不为空，不回发给发送此内容的客户端
if(targetchannel instanceof SocketChannel && targetchannel!=except)
{
SocketChannel dest = (SocketChannel)targetchannel;
dest.write(charset.encode(content));
}
}
}
public static void main(String[] args) throws IOException
{
new ChatRoomServer().init();
}
}
client代码
package com.huahuiyang.channel;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.SocketChannel;
import java.nio.charset.Charset;
import java.util.Iterator;
import java.util.Scanner;
import java.util.Set;
public class ChatRoomClient {
private Selector selector = null;
static final int port = 9999;
private Charset charset = Charset.forName("UTF-8");
private SocketChannel sc = null;
private String name = "";
private static String USER_EXIST = "system message: user exist, please change a name";
private static String USER_CONTENT_SPILIT = "#@#";
public void init() throws IOException
{
selector = Selector.open();
//连接远程主机的IP和端口
sc = SocketChannel.open(new InetSocketAddress("127.0.0.1",port));
sc.configureBlocking(false);
sc.register(selector, SelectionKey.OP_READ);
//开辟一个新线程来读取从服务器端的数据
new Thread(new ClientThread()).start();
//在主线程中 从键盘读取数据输入到服务器端
Scanner scan = new Scanner(System.in);
while(scan.hasNextLine())
{
String line = scan.nextLine();
if("".equals(line)) continue; //不允许发空消息
if("".equals(name)) {
name = line;
line = name+USER_CONTENT_SPILIT;
} else {
line = name+USER_CONTENT_SPILIT+line;
}
sc.write(charset.encode(line));//sc既能写也能读，这边是写
}
}
private class ClientThread implements Runnable
{
public void run()
{
try
{
while(true) {
int readyChannels = selector.select();
if(readyChannels == 0) continue;
Set selectedKeys = selector.selectedKeys(); //可以通过这个方法，知道可用通道的集合
Iterator keyIterator = selectedKeys.iterator();
while(keyIterator.hasNext()) {
SelectionKey sk = (SelectionKey) keyIterator.next();
keyIterator.remove();
dealWithSelectionKey(sk);
}
}
}
catch (IOException io)
{}
}
private void dealWithSelectionKey(SelectionKey sk) throws IOException {
if(sk.isReadable())
{
//使用 NIO 读取 Channel中的数据，这个和全局变量sc是一样的，因为只注册了一个SocketChannel
//sc既能写也能读，这边是读
SocketChannel sc = (SocketChannel)sk.channel();
ByteBuffer buff = ByteBuffer.allocate(1024);
String content = "";
while(sc.read(buff) > 0)
{
buff.flip();
content += charset.decode(buff);
}
//若系统发送通知名字已经存在，则需要换个昵称
if(USER_EXIST.equals(content)) {
name = "";
}
System.out.println(content);
sk.interestOps(SelectionKey.OP_READ);
}
}
}
public static void main(String[] args) throws IOException
{
new ChatRoomClient().init();
}
}
