服务端代码
public class Server_Test {
public static void main(String[] args) {
int port = 8080;
if (args != null && args.length > 0) {
try {
port = Integer.valueOf(args[0]);
} catch (NumberFormatException e) {
port = 8080;
}
}
MultiplexerTimeServer timeServer = new MultiplexerTimeServer(port);
new Thread(timeServer,"NIO-MultiplexerTimeServer-001").start();
}
}
class MultiplexerTimeServer implements Runnable {
private Selector selector;
private ServerSocketChannel servChannel;
private volatile boolean stop;
//初始化多路复用器，绑定监听端口
public MultiplexerTimeServer(int port) {
try {
//打开多路复用器
selector = Selector.open();
//打开服务器通道
servChannel = ServerSocketChannel.open();
//设置服务器通道为非阻塞模式
servChannel.configureBlocking(false);
//绑定端口,backlog指队列的容量，提供了容量限制的功能，避免太多客户端占用太多服务器资源
//serverSocketChannel有一个队列，存放没有来得及处理的客户端,服务器每次accept，就会从队列中去一个元素。
servChannel.socket().bind(new InetSocketAddress(port), 1024);
//把服务器通道注册到多路复用器上，并监听阻塞事件
servChannel.register(selector, SelectionKey.OP_ACCEPT);
System.out.println("The server is start in port: " + port);
} catch (IOException e) {
e.printStackTrace();
System.exit(1);
}
}
public void stop() {
this.stop = true;
}
@Override
public void run() {
while (!stop) {
try {
//多路复用器开始工作（轮询），选择已就绪的通道
//等待某个通道准备就绪时最多阻塞1秒，若超时则返回。
selector.select(1000);
Set<SelectionKey> selectionKeys = selector.selectedKeys();
Iterator<SelectionKey> it = selectionKeys.iterator();
SelectionKey key = null;
while (it.hasNext()) {
key = it.next();
it.remove();
try {
handleInput(key);
} catch (IOException e) {
if (key != null) {
key.cancel();
if (key.channel() != null) {
key.channel().close();
}
}
}
}
} catch (IOException e) {
e.printStackTrace();
}
}
//多路复用器关闭后，所有注册在上面的Channel和Pipe等资源都会自动去注册并关闭
//所以不需要重复释放资源
if (selector != null) {
try {
selector.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
private void handleInput(SelectionKey key) throws IOException {
if (key.isValid()) {
if (key.isAcceptable()) {
//获取服务器通道
ServerSocketChannel ssc = (ServerSocketChannel)key.channel();
//执行阻塞方法(等待客户端资源)
SocketChannel sc = ssc.accept();
//设置为非阻塞模式
sc.configureBlocking(false);
//注册到多路复用器上，并设置为可读状态
sc.register(selector, SelectionKey.OP_READ);
}
if (key.isReadable()) {
//读取数据
SocketChannel sc = (SocketChannel)key.channel();
ByteBuffer readBuffer = ByteBuffer.allocate(1024);
int readBytes = sc.read(readBuffer);
if (readBytes > 0) {
//反转缓冲区（复位）
readBuffer.flip();
byte[] bytes = new byte[readBuffer.remaining()];
//接受缓冲区数据
readBuffer.get(bytes);
//trim方法返回字符串的副本，忽略前导空白和尾部空白
String body = new String(bytes).trim();
// String body = new String(bytes, "UTF-8");
System.out.println("The time server receive order : " + body);
// String currentTime = "QUERY TIME ORDER"
// .equalsIgnoreCase(body) ? new java.util.Date
// (System.currentTimeMillis()).toString()
// : "BAD ORDER";
String currentTime = new Date(System.currentTimeMillis()).toString();
//给客户端回写数据
doWrite(sc, currentTime);
} else if (readBytes < 0) {
//对端链路关闭
key.cancel();
sc.close();
}
}
}
}
private void doWrite(SocketChannel channel, String response) throws IOException{
if (response != null && response.trim().length() > 0) {
System.out.println(response);
byte[] bytes = response.getBytes();
ByteBuffer writeBuffer = ByteBuffer.allocate(bytes.length);
writeBuffer.put(bytes);
writeBuffer.flip();
channel.write(writeBuffer);
}
}
}
程序看烦了吧！来看看这张图帮助你理解程序
服务端通信序列图：
其实，主要步骤可以分为
- Selector.open()：打开一个Selector。
- ServerSocketChannel.open()：创建服务端的Channel。
- bind()：绑定到某个端口上。并配置非阻塞模式。
- register()：注册Channel和关注的事件到Selector上。
- select()：拿到已经就绪的事件。
客户端代码
public class Client_Test {
public static void main(String[] args) throws UnknownHostException {
int port = 8080;
if (args != null && args.length > 0) {
try {
port = Integer.valueOf(args[0]);
} catch (NumberFormatException e) {
port = 8080;
}
}
new Thread(new TimeClientHandle("127.0.0.1", port), "Time-Client-001").start();
}
}
class TimeClientHandle implements Runnable{
private String host;
private int port;
private Selector selector;
private SocketChannel socketChannel;
//默认boolean值为false
private volatile boolean stop;
public TimeClientHandle(String host, int port) {
//host若为空，则设置为指定ip
this.host = host == null ? "127.0.0.1" : host;
this.port = port;
try {
//打开多路复用器
selector = Selector.open();
//打开管道
socketChannel = SocketChannel.open();
//设置管道为非阻塞模式
socketChannel.configureBlocking(false);
} catch (IOException e) {
e.printStackTrace();
System.exit(1);
}
}
@Override
public void run() {
try {
doConnect();
} catch (Exception e) {
e.printStackTrace();
System.exit(1);
}
while (!stop) {
try {
//阻塞等待1s，若超时则返回
selector.select(1000);
//获取所有selectionkey
Set<SelectionKey> selectionKeys = selector.selectedKeys();
//遍历所有selectionkey
Iterator<SelectionKey> it = selectionKeys.iterator();
SelectionKey key = null;
while (it.hasNext()) {
key = it.next();
//获取之后删除
it.remove();
try {
//处理该selectionkey
handleInput(key);
} catch (Exception e) {
if (key != null) {
//取消selectionkey
key.cancel();
if (key.channel() != null) {
//关闭该通道
key.channel().close();
}
}
}
}
} catch (IOException e) {
e.printStackTrace();
System.exit(1);
}
}
if (selector != null) {
try {
//关闭多路复用器
selector.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
public void handleInput(SelectionKey key) throws IOException{
//若该selectorkey可用
if (key.isValid()) {
//将key转型为SocketChannel
SocketChannel sc = (SocketChannel) key.channel();
//判断是否连接成功
if (key.isConnectable()) {
//若已经建立连接
if (sc.finishConnect()) {
//向多路复用器注册可读事件
sc.register(selector, SelectionKey.OP_READ);
//向管道写数据
doWrite(sc);
}else {
//连接失败 进程退出
System.exit(1);
}
}
//若是可读的事件
if (key.isReadable()) {
//创建一个缓冲区
ByteBuffer readBuffer = ByteBuffer.allocate(1024);
System.out.println("before : "+readBuffer);
//从管道中读取数据然后写入缓冲区中
int readBytes = sc.read(readBuffer);
System.out.println("after : "+readBuffer);
//若有数据
if (readBytes > 0) {
//反转缓冲区
readBuffer.flip();
System.out.println(readBuffer);
byte[] bytes = new byte[readBuffer.remaining()];
//获取缓冲区并写入字节数组中
readBuffer.get(bytes);
//将字节数组转换为String类型
String body = new String(bytes);
System.out.println(body.length());
System.out.println("Now is : " + body + "!");
this.stop = true;
} else if (readBytes < 0) {
key.cancel();
sc.close();
} else {
sc.register(selector, SelectionKey.OP_READ);
}
}
}
}
public void doConnect() throws IOException {
//通过ip和端口号连接到服务器
if (socketChannel.connect(new InetSocketAddress(host, port))) {
//向多路复用器注册可读事件
socketChannel.register(selector, SelectionKey.OP_READ);
//向管道写数据
doWrite(socketChannel);
} else {
//若连接服务器失败,则向多路复用器注册连接事件
socketChannel.register(selector, SelectionKey.OP_CONNECT);
}
}
private void doWrite(SocketChannel sc) throws IOException {
//要写的内容
byte[] req = " - QUERY TIME ORDER - ".getBytes();
//为字节缓冲区分配指定字节大小的容量
ByteBuffer writeBuffer = ByteBuffer.allocate(req.length);
//将内容写入缓冲区
writeBuffer.put(req);
//反转缓冲区
writeBuffer.flip();
//输出打印缓冲区的可读大小
System.out.println(writeBuffer.remaining());
//将内容写入管道中
sc.write(writeBuffer);
if (!writeBuffer.hasRemaining()) {
//若缓冲区中无可读字节，则说明成功发送给服务器消息
System.out.println("Send order 2 server succeed.");
}
}
}
程序看烦了吧！来看看这张图帮助你理解程序
客户端通信序列图：
服务端运行结果：
客户端运行结果
小结：
首先恭喜你看完了“这么麻烦”的CS代码，和BIO相比，NIO的代码确实复杂了很多，但是不是就意味着我们必须要编写这么复杂的业务代码呢？答案是否定的，我感觉直接使用NIO编程，容易出错，尤其是要读写转换时要反转缓冲区，那么一个好的解决方法油然而生，那就是Netty，一个基于事件驱动的网络框架。