Java网络编程——使用NIO实现非阻塞Socket通信

转自：https://blog.csdn.net/yanmei_yao/article/details/8586199

除了普通的Socket与ServerSocket实现的阻塞式通信外，java提供了非阻塞式通信的NIO API。先看一下NIO的实现原理。

从图中可以看出，服务器上所有Channel（包括ServerSocketChannel和SocketChannel）都需要向Selector注册，而该Selector则负责监视这些Socket的IO状态，当其中任意一个或者多个Channel具有可用的IO操作时，该Selector的select()方法将会返回大于0的整数，该整数值就表示该Selector上有多少个Channel具有可用的IO操作，并提供了selectedKeys（）方法来返回这些Channel对应的SelectionKey集合。正是通过Selector，使得服务器端只需要不断地调用Selector实例的select()方法即可知道当前所有Channel是否有需要处理的IO操作。

看个demo

NClient.java

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;
public class Server {
public static void main(String[] args) {
int port = 8082;
int backlog = 3000;
Charset charSet = Charset.forName(“UTF-8″);
try {
Selector selector = Selector.open();
ServerSocketChannel channel = ServerSocketChannel.open();
channel.bind(new InetSocketAddress(“localhost”,port), backlog);
channel.configureBlocking(false);
channel.register(selector, SelectionKey.OP_ACCEPT);
while(selector.select()>0){
for(SelectionKey sk:selector.selectedKeys()){
//移除，TODO
selector.selectedKeys().remove(sk);
if(sk.isAcceptable()){
ServerSocketChannel ssc = (ServerSocketChannel) sk.channel();
//SocketChannel sc = channel.accept();
SocketChannel sc = ssc.accept();
sc.configureBlocking(false);
sc.register(selector, SelectionKey.OP_READ);
sk.interestOps(SelectionKey.OP_ACCEPT);
}
if(sk.isReadable()){
SocketChannel saChannel = (SocketChannel) sk.channel();
ByteBuffer buffer = ByteBuffer.allocate(1024);
String content = “”;
while(saChannel.read(buffer)>0){
buffer.flip();
content = content + charSet.decode(buffer);
}
System.out.println(“读取到的数据为：”+content);
sk.interestOps(SelectionKey.OP_READ);
if(content!=null&&!”".equals(content)){
for(SelectionKey sko:selector.keys()){
Channel targetChannel = sko.channel();
if(targetChannel instanceof SocketChannel){
SocketChannel tc = (SocketChannel) targetChannel;
tc.write(charSet.encode(content));
}
}
}
}
}
}
} catch (IOException e) {
e.printStackTrace();
}
}
}

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.Scanner;
public class NClient {
//定义检测SocketChannel的Selector对象
private Selector selector=null;
//定义处理编码和解码的字符集
private Charset charset=Charset.forName("UTF-8");
//客户端SocketChannel
private SocketChannel sc=null;
public void init() throws IOException{
selector=Selector.open();
InetSocketAddress isa=new InetSocketAddress("127.0.0.1",30000);
//调用open静态方法创建连接到指定主机的SocketChannel
sc=SocketChannel.open(isa);
//设置该sc以非阻塞方式工作
sc.configureBlocking(false);
//将Socketchannel对象注册到指定Selector
sc.register(selector, SelectionKey.OP_READ);
//启动读取服务器端数据的线程
new ClientThread().start();
//创建键盘输入流
Scanner scan=new Scanner(System.in);
while(scan.hasNextLine()){
//读取键盘输入
String line=scan.nextLine();
//将键盘输入的内容输出到SocketChannel中
sc.write(charset.encode(line));
}
}
//定义读取服务器数据的线程
private class ClientThread extends Thread{
public void run(){
try{
while(selector.select()>0){
//遍历每个有可用IO操作Channel对应的SelectionKey
for(SelectionKey sk:selector.selectedKeys()){
//删除正在处理的SelectionKey
selector.selectedKeys().remove(sk);
//如果该SelectionKey对应的Channel中有可读的数据
if(sk.isReadable()){
//使用NIO读取channel中的数据
SocketChannel sc=(SocketChannel) sk.channel();
ByteBuffer buff=ByteBuffer.allocate(1024);
String content="";
while(sc.read(buff)>0){
//sc.read(buff);
buff.flip();
content+=charset.decode(buff);
}
//打印输出读取的内容
System.out.println("聊天信息"+content);
//为下一次读取做准备
sk.interestOps(SelectionKey.OP_READ);
}
}
}
}catch(IOException ex){
ex.printStackTrace();
}
}
}
public static void main(String[]args) throws IOException{
new NClient().init();
}
}

NServer.java

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.Scanner;
public class Client {
private static Charset charSet = Charset.forName(“UTF-8″);
public static void main(String[] args) {
int port = 8082;
try {
Selector selector = Selector.open();
SocketChannel socketChannel = SocketChannel.open();
socketChannel.connect(new InetSocketAddress(“localhost”, port));
socketChannel.configureBlocking(false);
socketChannel.register(selector, SelectionKey.OP_READ);
Scanner scanner = new Scanner(System.in);
new ReadMsg(selector).start();
while(scanner.hasNextLine()){
String line = scanner.nextLine();
socketChannel.write(charSet.encode(line));
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
class ReadMsg extends Thread{
private static Charset charSet = Charset.forName(“UTF-8″);
private Selector selector;
public ReadMsg(Selector selector){
this.selector = selector;
}
@Override
public void run() {
try {
while(selector.select()>0){
for(SelectionKey sk:selector.selectedKeys()){
selector.selectedKeys().remove(sk);
if(sk.isConnectable()){
SocketChannel channel = (SocketChannel) sk.channel();
if(channel.isConnectionPending()){
channel.finishConnect();
}
channel.configureBlocking(false);
channel.register(selector, SelectionKey.OP_READ);
sk.interestOps(SelectionKey.OP_READ);
}
if(sk.isReadable()){
String content = “”;
ByteBuffer buffer = ByteBuffer.allocate(1024);
SocketChannel channel = (SocketChannel) sk.channel();
while(channel.read(buffer)>0){
buffer.flip();
content = content+charSet.decode(buffer);
}
System.out.println(“接收到的信息：”+content);
sk.interestOps(SelectionKey.OP_READ);
}
}
}
} catch (IOException e) {
e.printStackTrace();
}
}
}

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;
public class NServer {
//用于检测所有Channel状态的Selector
private Selector selector=null;
//定义实现编码、解码的字符集对象
private Charset charset=Charset.forName("UTF-8");
public void init() throws IOException{
selector=Selector.open();
//通过open方法来打开一个未绑定的ServerSocketChannel实例
ServerSocketChannel server=ServerSocketChannel.open();
InetSocketAddress isa=new InetSocketAddress("127.0.0.1",30000);
//将该ServerSocketChannel绑定到指定ip地址
server.socket().bind(isa);
//设置ServerSocket以非阻塞方式工作
server.configureBlocking(false);
//将server注册到指定Selector对象
server.register(selector, SelectionKey.OP_ACCEPT);
while(selector.select()>0){
//依次处理selector上的每个已选择的SelectionKey
for(SelectionKey sk:selector.selectedKeys()){
//从selector上的已选择Key集中删除正在处理的SelectionKey
selector.selectedKeys().remove(sk);
//如果sk对应的通信包含客户端的连接请求
if(sk.isAcceptable()){
//调用accept方法接受连接，产生服务器端对应的SocketChannel
SocketChannel sc=server.accept();
//设置采用非阻塞模式
sc.configureBlocking(false);
sc.register(selector, SelectionKey.OP_READ);
//将sk对应的Channel设置成准备接受其他请求
sk.interestOps(SelectionKey.OP_ACCEPT);
}
//如果sk对应的通道有数据需要读取
if(sk.isReadable()){
//获取该SelectionKey对应的Channel，该Channel中有可读的数据
SocketChannel sc=(SocketChannel) sk.channel();
//定义准备之星读取数据的ByteBuffer
ByteBuffer buff=ByteBuffer.allocate(1024);
String content="";
//开始读取数据
try{
while(sc.read(buff)>0){
buff.flip();
content+=charset.decode(buff);
}
//打印从该sk对应的Channel里读到的数据
System.out.println("=========="+content);
//将sk对应的Channel设置成准备下一次读取
sk.interestOps(SelectionKey.OP_READ);
//如果捕捉到该sk对应的channel出现异常，即表明该channel对应的client出现了
//异常，所以从selector中取消sk的注册
}catch(IOException e){
//从Selector中删除指定的SelectionKey
sk.cancel();
if(sk.channel()!=null){
sk.channel().close();
}
}
//如果content的长度大于0，即聊天信息不为空
if(content.length()>0){
//遍历该selector里注册的所有SelectKey
for(SelectionKey key:selector.keys()){
//选取该key对应的Channel
Channel targetChannel=key.channel();
//如果该channel是SocketChannel对象
if(targetChannel instanceof SocketChannel){
//将独到的内容写入该Channel中
SocketChannel dest=(SocketChannel) targetChannel;
dest.write(charset.encode(content));
}
}
}
}
}
}
}
public static void main(String[]args) throws IOException{
new NServer().init();
}
}

通过java提供的NIO实现非阻塞Socket通信，大大提高了网络服务器的性能。

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Java网络编程——使用NIO实现非阻塞Socket通信

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