网络编程-BIO、NIO、AIO

基本概念

Socket又称“套接字”，应用程序通常通过“套接字”向网络发出请求或者应答网络请求。

Socket类库位于java.net包中，ServerSocket用于服务器端，Socket是建立网络连接时使用的。在连接成功时，应用程序两端都会产生一个Socket实例，操作这个实例，完成所需的会话。对于一个网络连接来说，套接字是平等的，不因为在服务器端或在客户端而产生不同级别。不管是Socket还是ServerSocket都是通过SocketImpl类及子类完成的。

Socket通信四步骤：

1. 服务器监听,是服务器端套接字并不定位具体的客户端套接字，而是处于等待连接的状态，实时监控网络状态。

2. 客户端请求，由客户端的套接字提出连接请求，要连接的目标是服务器端的套接字。客户端的套接字必须首先描述它要连接的服务器的套接字，指出服务器套接字的地址和端口号，然后就向服务器端套接字提出连接请求。

3. 服务器端连接确认，服务器端套接字监听到或者接收到客户端套接字的连接请求，它就响应客户端套接字的请求，建立一个新的线程，把服务器端套接字的描述发给客户端。

4. 客户端连接确认，一旦客户端确认了此描述，连接就建立好了。双方开始进行通信，而服务器端套接字继续处于监听状态，继续接收其他客户端套接字的连接请求。

public class Server {

final static int PORT = 6666;

public static void main(String[] args) {
ServerSocket server = null;
try {
server = new ServerSocket(PORT);
System.out.println("server start..");
//进行阻塞
Socket socket = server.accept();
//新建一个线程执行客户端任务
new Thread(new ServerHandler(socket)).start();;
} catch (IOException e) {
e.printStackTrace();
} finally {
if (server != null) {
try {
server.close();
} catch (IOException e) {
e.printStackTrace();
}
}
server = null;
}

}
}

public class Client {

final static String ADDRESS = "127.0.0.1";
final static int PORT = 6666;

public static void main(String[] args) {
Socket socket = null;
BufferedReader in = null;
PrintWriter out = null;

try {
socket = new Socket(ADDRESS,PORT);
in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
out = new PrintWriter(socket.getOutputStream(),true);

//向服务端发送数据
out.println("接收到客户端请求数据..");
String response = in.readLine();
System.out.println("Client:" + response);
} catch (IOException e) {
e.printStackTrace();
} finally {
if(in != null){
try {
in.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (out != null) {
out.close();
}
if (socket != null) {
try {
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
in = null;
out = null;
socket = null;
}
}
}

伪异步IO，采用线程池和任务队列可以实现一种伪异步的IO通信框架。将客户端的socket封装成一个task任务（实现runnable接口的类）然后投递到线程池中，配置相应的队列进行实现。

阻塞：应用程序在获取网络数据的时候，如果网络传输数据很慢，那么程序就一直等待，直到传输完毕为止。

非阻塞：应用程序直接可以获取已经准备就绪好的数据，无需等待。

同步：应用程序会直接参与IO读写操作，并且我们的应用程序会直接阻塞到某一个方法上，直到数据准备就绪，或者采用轮询的策略实时检查数据的就绪状态，如果就绪则获取数据。

异步时，则所有的IO读写操作交给操作系统处理，与我们的应用程序没有直接关系，我们程序不需要关心IO读写，当操作系统完成了IO读写操作时，会给我们应用程序发送通知，应用程序直接拿走数据即可。

BIO为同步阻塞，NIO为同步非阻塞，AIO为异步非阻塞。

Buffer是一个对象，它包含一些要写入或者要读取的数据。在NIO类库中加入Buffer对象，体现了新库与原IO的的一个重要的区别。在面向流的IO中，可以将数据直接写入或读取到Stream对象中。在NIO库中，所有数据都是用缓冲区处理的（读写）。缓冲区实质上是一个数组，通常是一个字节数组（ByteBuffer），也可以使用其他类型的数组。这个数组为缓冲区提供了数据的访问读写等操作属性，如位置、容量、上限等概念。

IntBuffer buffer = IntBuffer.allocate(10);
buffer.put(6);
buffer.put(8);
buffer.put(10);
buffer.flip();//buffer位置复位

System.out.println("使用flip复位：" + buffer);
System.out.println("容量为：" + buffer.capacity());
System.out.println("限制为：" + buffer.limit());

System.out.println("获取下标为1的元素：" + buffer.get(1));
System.out.println("get(index)方法，position位置不改变：" + buffer);
buffer.put(1, 4);
System.out.println("put(index,change)方法，position位置不变：" + buffer);

for (int i = 0; i < buffer.limit(); i++) {
//调用get方法会使其缓冲区位置（position）向后递增一位
System.out.println(buffer.get());
}
System.out.println("buffer对象遍历之后为：" + buffer);

//wrap方法使用
int[] arr = new int[]{1,2,3};
IntBuffer buffer = IntBuffer.wrap(arr);
System.out.println(buffer);

IntBuffer intBuffer = IntBuffer.wrap(arr, 0, 2);
//容量为数组arr的长度，但是可操作的元素只有实际进入缓存区的元素长度
System.out.println(intBuffer);*

IntBuffer buffer = IntBuffer.allocate(10);
int[] arr = new int[]{1,2,3};
buffer.put(arr);
System.out.println(buffer);
//一种复制方法
IntBuffer intBuffer = buffer.duplicate();
System.out.println(intBuffer);

//设置buffer的位置属性
//      buffer.position(0);
buffer.flip();//复位
System.out.println(buffer);

System.out.println("可读数据为：" + buffer.remaining());
int[] arr2 = new int[buffer.remaining()];
//将缓冲区数据放入arr2中去
buffer.get(arr2);
for (int i : arr2) {
System.out.print(Integer.toString(i) + ",");
}

BIO编程

public class ServerHandler1 implements Runnable {

private Socket socket;
public ServerHandler1(Socket socket) {
this.socket = socket;
}

@Override
public void run() {
BufferedReader br = null ;
PrintWriter pw = null;
try {
br = new BufferedReader(new InputStreamReader(socket.getInputStream()));
pw = new PrintWriter(socket.getOutputStream(),true);
String body = null;
while (true) {
body = br.readLine();
if (body == null) {
break;
}
System.out.println("server:" + body);
pw.println("服务端回应数据");
}
} catch (IOException e) {
e.printStackTrace();
} finally {
if (br != null) {
try {
br.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}

}

public class Server1 {

private final static int PORT = 6666;
public static void main(String[] args) {
ServerSocket serverSocket = null;
Socket socket = null;
try {
//创建serverSocket
serverSocket = new ServerSocket(PORT);
System.out.println("server start");
//阻塞
socket = serverSocket.accept();
new Thread(new ServerHandler1(socket)).start();
} catch (IOException e) {
e.printStackTrace();
} finally {
if(serverSocket != null){
try {
serverSocket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
}

public class Client1 {

private final static String ADDRESS = "127.0.0.1";
private final static int PORT = 6666;

public static void main(String[] args) {
BufferedReader br = null;
PrintWriter pw = null;
Socket socket = null;
try {
//创建socket
socket = new Socket(ADDRESS, PORT);
br = new BufferedReader(new InputStreamReader(socket.getInputStream()));
pw = new PrintWriter(socket.getOutputStream(),true);
pw.println("客户端向服务端发送信息");
String readLine = br.readLine();
System.out.println(readLine);
} catch (IOException e) {
e.printStackTrace();
} finally {
if (pw != null) {
pw.close();
}
if (br != null) {
try {
br.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if(socket != null){
try {
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}

}

伪异步

public class ServerHandler1 implements Runnable{

private Socket socket;
public ServerHandler1(Socket socket) {
this.socket = socket;
}

@Override
public void run() {
BufferedReader in = null;
PrintWriter out = null;
try {
in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
out = new PrintWriter(socket.getOutputStream(),true);
String body = null;
while (true) {
body = in.readLine();
if(body == null) break;
System.out.println("客户端发送信息： " + body);
out.println("server response");
}
} catch (IOException e) {
e.printStackTrace();
} finally {
if (in != null) {
try {
in.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (out != null) {
out.close();
}
if (socket != null) {
try {
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
socket = null;
}
}

}

//自定义线程池
public class HandlerExecutorPool1 {

private ExecutorService executors;
public HandlerExecutorPool1(int maxPoolSize, int queueSize) {
this.executors = new ThreadPoolExecutor(
Runtime.getRuntime().availableProcessors(),
maxPoolSize, 120L,
TimeUnit.SECONDS,
new ArrayBlockingQueue<Runnable>(queueSize));
}

public void execute(Runnable task){
this.executors.submit(task);
}
}

//服务端
public class Server1 {

final static int PORT = 6666;
public static void main(String[] args) {
try {
ServerSocket serverSocket = new ServerSocket(PORT);
System.out.println("server start");
HandlerExecutorPool1 pool = new HandlerExecutorPool1(50,1000);
Socket socket = null;
while (true) {
socket = serverSocket.accept();
pool.execute(new ServerHandler1(socket));
}
} catch (IOException e) {
e.printStackTrace();
}
}
}

//客户端
public class Client1 {

final static String ADDRESS = "127.0.0.1";
final static int PORT = 6666;

public static void main(String[] args) {
BufferedReader in = null;
PrintWriter out = null;
Socket socket = null;
try {
socket = new Socket(ADDRESS, PORT);
in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
out = new PrintWriter(socket.getOutputStream(),true);
out.println("client response");
String response = in.readLine();
System.out.println("服务端发送的信息：" + response);
} catch (IOException e) {
e.printStackTrace();
} finally {
if (in != null) {
try {
in.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (out != null) {
out.close();
}
if (socket != null) {
try {
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
socket = null;
}
}
}
}

NIO编程

public class Server1 implements Runnable{
//1 多路复用器（管理所有的通道）
private Selector seletor;
//2 建立缓冲区
private ByteBuffer readBuf = ByteBuffer.allocate(1024);
//3
private ByteBuffer writeBuf = ByteBuffer.allocate(1024);
public Server1(int port){
try {
//1 打开路复用器
this.seletor = Selector.open();
//2 打开服务器通道
ServerSocketChannel ssc = ServerSocketChannel.open();
//3 设置服务器通道为非阻塞模式
ssc.configureBlocking(false);
//4 绑定地址
ssc.bind(new InetSocketAddress(port));
//5 把服务器通道注册到多路复用器上，并且监听阻塞事件
ssc.register(this.seletor, SelectionKey.OP_ACCEPT);

System.out.println("Server start, port :" + port);

} catch (IOException e) {
e.printStackTrace();
}
}

@Override
public void run() {
while(true){
try {
//1 必须要让多路复用器开始监听
this.seletor.select();
//2 返回多路复用器已经选择的结果集
Iterator<SelectionKey> keys = this.seletor.selectedKeys().iterator();
//3 进行遍历
while(keys.hasNext()){
//4 获取一个选择的元素
SelectionKey key = keys.next();
//5 直接从容器中移除就可以了
keys.remove();
//6 如果是有效的
if(key.isValid()){
//7 如果为阻塞状态
if(key.isAcceptable()){
this.accept(key);
}
//8 如果为可读状态
if(key.isReadable()){
this.read(key);
}
//9 写数据
if(key.isWritable()){
//this.write(key); //ssc
}
}

}
} catch (IOException e) {
e.printStackTrace();
}
}
}

private void write(SelectionKey key){
//ServerSocketChannel ssc =  (ServerSocketChannel) key.channel();
//ssc.register(this.seletor, SelectionKey.OP_WRITE);
}

private void read(SelectionKey key) {
try {
//1 清空缓冲区旧的数据
this.readBuf.clear();
//2 获取之前注册的socket通道对象
SocketChannel sc = (SocketChannel) key.channel();
//3 读取数据
int count = sc.read(this.readBuf);
//4 如果没有数据
if(count == -1){
key.channel().close();
key.cancel();
return;
}
//5 有数据则进行读取 读取之前需要进行复位方法(把position 和limit进行复位)
this.readBuf.flip();
//6 根据缓冲区的数据长度创建相应大小的byte数组，接收缓冲区的数据
byte[] bytes = new byte[this.readBuf.remaining()];
//7 接收缓冲区数据
this.readBuf.get(bytes);
//8 打印结果
String body = new String(bytes).trim();
System.out.println("Server : " + body);

// 9..可以写回给客户端数据

} catch (IOException e) {
e.printStackTrace();
}

}

private void accept(SelectionKey key) {
try {
//1 获取服务通道
ServerSocketChannel ssc =  (ServerSocketChannel) key.channel();
//2 执行阻塞方法
SocketChannel sc = ssc.accept();
//3 设置阻塞模式
sc.configureBlocking(false);
//4 注册到多路复用器上，并设置读取标识
sc.register(this.seletor, SelectionKey.OP_READ);
} catch (IOException e) {
e.printStackTrace();
}
}

public static void main(String[] args) {

new Thread(new Server1(8765)).start();;
}

}

public class Client1 {

//需要一个Selector
public static void main(String[] args) {

//创建连接的地址
InetSocketAddress address = new InetSocketAddress("127.0.0.1", 8765);

//声明连接通道
SocketChannel sc = null;

//建立缓冲区
ByteBuffer buf = ByteBuffer.allocate(1024);

try {
//打开通道
sc = SocketChannel.open();
//进行连接
sc.connect(address);

while(true){
//定义一个字节数组，然后使用系统录入功能：
byte[] bytes = new byte[1024];
System.in.read(bytes);

//把数据放到缓冲区中
buf.put(bytes);
//对缓冲区进行复位
buf.flip();
//写出数据
sc.write(buf);
//清空缓冲区数据
buf.clear();
}
} catch (IOException e) {
e.printStackTrace();
} finally {
if(sc != null){
try {
sc.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}

}

}

AIO编程，在NIO基础之上引入了异步通道，并提供了异步文件和异步套接字通道的实现。

- AsynchronousServerScoketChannel

- AsynchronousScoketChanel

public class ServerCompletionHandler implements CompletionHandler<AsynchronousSocketChannel, Server> {

@Override
public void completed(AsynchronousSocketChannel asc, Server attachment) {
//当有下一个客户端接入的时候 直接调用Server的accept方法，这样反复执行下去，保证多个客户端都可以阻塞
attachment.assc.accept(attachment, this);
read(asc);
}

private void read(final AsynchronousSocketChannel asc) {
//读取数据
ByteBuffer buf = ByteBuffer.allocate(1024);
asc.read(buf, buf, new CompletionHandler<Integer, ByteBuffer>() {
@Override
public void completed(Integer resultSize, ByteBuffer attachment) {
//进行读取之后,重置标识位
attachment.flip();
//获得读取的字节数
System.out.println("Server -> " + "收到客户端的数据长度为:" + resultSize);
//获取读取的数据
String resultData = new String(attachment.array()).trim();
System.out.println("Server -> " + "收到客户端的数据信息为:" + resultData);
String response = "服务器响应, 收到了客户端发来的数据: " + resultData;
write(asc, response);
}
@Override
public void failed(Throwable exc, ByteBuffer attachment) {
exc.printStackTrace();
}
});
}

private void write(AsynchronousSocketChannel asc, String response) {
try {
ByteBuffer buf = ByteBuffer.allocate(1024);
buf.put(response.getBytes());
buf.flip();
asc.write(buf).get();
} catch (InterruptedException e) {
e.printStackTrace();
} catch (ExecutionException e) {
e.printStackTrace();
}
}

@Override
public void failed(Throwable exc, Server attachment) {
exc.printStackTrace();
}

}

public class Server {
//线程池
private ExecutorService executorService;
//线程组
private AsynchronousChannelGroup threadGroup;
//服务器通道
public AsynchronousServerSocketChannel assc;

public Server(int port){
try {
//创建一个缓存池
executorService = Executors.newCachedThreadPool();
//创建线程组
threadGroup = AsynchronousChannelGroup.withCachedThreadPool(executorService, 1);
//创建服务器通道
assc = AsynchronousServerSocketChannel.open(threadGroup);
//进行绑定
assc.bind(new InetSocketAddress(port));

System.out.println("server start , port : " + port);
//进行阻塞
assc.accept(this, new ServerCompletionHandler());
//一直阻塞 不让服务器停止
Thread.sleep(Integer.MAX_VALUE);

} catch (Exception e) {
e.printStackTrace();
}
}

public static void main(String[] args) {
Server server = new Server(8765);
}

}

public class Client implements Runnable{

private AsynchronousSocketChannel asc ;

public Client() throws Exception {
asc = AsynchronousSocketChannel.open();
}

public void connect(){
asc.connect(new InetSocketAddress("127.0.0.1", 8765));
}

public void write(String request){
try {
asc.write(ByteBuffer.wrap(request.getBytes())).get();
read();
} catch (Exception e) {
e.printStackTrace();
}
}

private void read() {
ByteBuffer buf = ByteBuffer.allocate(1024);
try {
asc.read(buf).get();
buf.flip();
byte[] respByte = new byte[buf.remaining()];
buf.get(respByte);
System.out.println(new String(respByte,"utf-8").trim());
} catch (InterruptedException e) {
e.printStackTrace();
} catch (ExecutionException e) {
e.printStackTrace();
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
}

@Override
public void run() {
while(true){

}
}

public static void main(String[] args) throws Exception {
Client c1 = new Client();
c1.connect();

Client c2 = new Client();
c2.connect();

Client c3 = new Client();
c3.connect();

new Thread(c1, "c1").start();
new Thread(c2, "c2").start();
new Thread(c3, "c3").start();

Thread.sleep(1000);

c1.write("c1 aaa");
c2.write("c2 bbbb");
c3.write("c3 ccccc");
}

}