今天突然间想用nio实现个Echo服务,程序实现起来实现不算困难,但跑起来后,在Server端的ServerSocket完成accept之后,我的CPU总是跳到100%。嗯,小郁闷,后来,才发现自己在Server端注册了多余的监听事件SelectionKey.OP_WRITE,改过来后好多了,希望记住这个教训。
EchoServer.java
- package edu.dlut.zxf.nio;
- import java.io.IOException;
- import java.net.InetAddress;
- import java.net.InetSocketAddress;
- import java.nio.ByteBuffer;
- import java.nio.channels.SelectionKey;
- import java.nio.channels.Selector;
- import java.nio.channels.ServerSocketChannel;
- import java.nio.channels.SocketChannel;
- import java.util.Set;
- /**
- * Echo服务器
- * @author finux
- */
- public class EchoServer {
- public final static int BUFFER_SIZE = 1024; //默认端口
- public final static String HOST = "210.30.107.17";
- public final static int PORT = 8888;
- public static void main(String[] args) {
- ServerSocketChannel ssc = null;
- //缓冲区
- ByteBuffer buffer = ByteBuffer.allocate(BUFFER_SIZE);
- Selector selector = null;
- try {
- selector = Selector.open();
- ssc = ServerSocketChannel.open();
- ssc.socket().bind(new InetSocketAddress(InetAddress.getByName(HOST), PORT));
- ssc.configureBlocking(false);
- ssc.register(selector, SelectionKey.OP_ACCEPT);
- print("服务器启动,准备好连接...");
- while (selector.select() > 0) {
- Set<SelectionKey> selectionKeys = selector.selectedKeys();
- for (SelectionKey key: selectionKeys) {
- if (key.isAcceptable()) {
- SocketChannel sc = ssc.accept();
- print("有新的连接!地址:" + sc.socket().getRemoteSocketAddress());
- sc.configureBlocking(false);
- sc.register(selector, SelectionKey.OP_READ);
- // 不要写成:
- // sc.register(selector, SelectionKey.OP_READ | SelectionKey.OP_WRITE);
- // 毕竟这样多注册的无用的事件SelectionKey.OP_WRTE
- // 如果是这样,在完成accept后,CPU也许会跑到100%
- }
- //same to if ((ops & SelectionKey.OP_READ) == SelectionKey.OP_READ) {
- if (key.isReadable()) {
- SocketChannel sc = (SocketChannel)key.channel();
- print("有新的读取!地址:" + sc.socket().getRemoteSocketAddress());
- buffer.clear();
- sc.read(buffer);
- buffer.flip();
- byte[] b = new byte[buffer.limit()];
- buffer.get(b);
- String s = new String(b);
- if (s.equals("bye")) {
- print("断开连接:" + sc.socket().getRemoteSocketAddress());
- //断开连接后,取消此键的通道到其选择器的注册
- key.cancel();
- sc.close();
- continue;
- }
- print("读取的内容为:" + s);
- buffer.clear();
- s = "echo: " + s;
- buffer.put(s.getBytes());
- buffer.flip();
- sc.write(buffer);
- }
- }
- selectionKeys.clear();
- }
- } catch(IOException e) {
- e.printStackTrace();
- }
- }
- private static void print(String s) {
- System.out.println(s);
- }
- }
EchoClient.java
- package edu.dlut.zxf.nio;
- import java.util.Set;
- import java.io.BufferedReader;
- import java.io.IOException;
- import java.io.InputStreamReader;
- import java.net.InetSocketAddress;
- import java.net.InetAddress;
- import java.nio.ByteBuffer;
- import java.nio.channels.SelectionKey;
- import java.nio.channels.Selector;
- import java.nio.channels.SocketChannel;
- /**
- * Echo客户端
- * @author finux
- */
- public class EchoClient {
- public static void main(String[] args) {
- ByteBuffer buffer = ByteBuffer.allocate(EchoServer.BUFFER_SIZE);
- Selector selector = null;
- SocketChannel sc = null;
- try {
- selector = Selector.open();
- sc = SocketChannel.open();
- sc.configureBlocking(false);
- sc.connect(new InetSocketAddress(InetAddress.getByName(EchoServer.HOST), EchoServer.PORT));
- print("客户端启动,准备连接...");
- if (sc.isConnectionPending()) {
- sc.finishConnect();
- }
- print("完成连接");
- sc.register(selector, SelectionKey.OP_READ | SelectionKey.OP_WRITE);
- boolean writed = false;
- boolean down = false;
- while (!down && selector.select() > 0) {
- Set<SelectionKey> selectionKeys = selector.selectedKeys();
- for (SelectionKey key: selectionKeys) {
- //int ops = key.readyOps();
- //if ((ops & SelectionKey.OP_WRITE) == SelectionKey.OP_WRITE && !writed) {
- if (key.isWritable() && !writed) {
- System.out.print("Input(bye to end): ");
- BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
- String s = br.readLine();
- if (s != null && !s.trim().equals("")) {
- buffer.clear();
- buffer.put(s.getBytes());
- buffer.flip();
- sc.write(buffer);
- writed = true;
- if (s.equals("bye")) {
- down = true;
- break;
- }
- }
- }
- //if ((ops & SelectionKey.OP_READ) == SelectionKey.OP_READ && writed) {
- if (key.isReadable() && writed) {
- buffer.clear();
- sc.read(buffer);
- buffer.flip();
- byte[] b = new byte[buffer.limit()];
- buffer.get(b);
- print(new String(b));
- writed = false;
- }
- }
- selectionKeys.clear();
- }
- } catch(IOException e) {
- e.printStackTrace();
- }
- }
- private static void print(String s) {
- System.out.println(s);
- }
- }
当然EchoClient也可以像下面这样来实现:
EchoClient2.java
- package edu.dlut.zxf.nio;
- import java.util.Set;
- import java.io.BufferedReader;
- import java.io.IOException;
- import java.io.InputStreamReader;
- import java.net.InetSocketAddress;
- import java.net.InetAddress;
- import java.nio.ByteBuffer;
- import java.nio.channels.SelectionKey;
- import java.nio.channels.Selector;
- import java.nio.channels.SocketChannel;
- /**
- * Echo客户端2
- * @author finux
- */
- public class EchoClient2 {
- public static void main(String[] args) {
- ByteBuffer buffer = ByteBuffer.allocate(EchoServer.BUFFER_SIZE);
- Selector selector = null;
- SocketChannel sc = null;
- try {
- selector = Selector.open();
- sc = SocketChannel.open();
- sc.configureBlocking(false);
- sc.register(selector, SelectionKey.OP_CONNECT);
- sc.connect(new InetSocketAddress(InetAddress.getByName(EchoServer.HOST), EchoServer.PORT));
- print("客户端启动,准备连接...");
- boolean writed = false;
- boolean down = false;
- while (!down && selector.select() > 0) {
- Set<SelectionKey> selectionKeys = selector.selectedKeys();
- for (SelectionKey key: selectionKeys) {
- //int ops = key.readyOps();
- //if ((ops & SelectionKey.OP_CONNECT) == SelectionKey.OP_CONNECT) {
- if (key.isConnectable()) {
- print("完成连接!");
- if (sc.isConnectionPending()) {
- sc.finishConnect();
- }
- sc.register(selector, SelectionKey.OP_READ | SelectionKey.OP_WRITE);
- }
- //if ((ops & SelectionKey.OP_WRITE) == SelectionKey.OP_WRITE && !writed) {
- if (key.isWritable() && !writed) {
- //从准备IO中读取内容
- System.out.print("Input(bye to end): ");
- BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
- String s = br.readLine();
- if (s != null && !s.trim().equals("")) {
- buffer.clear();
- buffer.put(s.getBytes());
- buffer.flip();
- sc.write(buffer);
- writed = true;
- if (s.equals("bye")) {
- down = true;
- break;
- }
- }
- }
- //if ((ops & SelectionKey.OP_READ) == SelectionKey.OP_READ && writed) {
- if (key.isReadable() && writed) {
- buffer.clear();
- sc.read(buffer);
- buffer.flip();
- byte[] b = new byte[buffer.limit()];
- buffer.get(b);
- print(new String(b));
- writed = false;
- }
- }
- selectionKeys.clear();
- }
- } catch(IOException e) {
- e.printStackTrace();
- }
- }
- private static void print(String s) {
- System.out.println(s);
- }
- }
但是这样的话,显然EchoClient2中的while循环中的for循环(若有n次),在每次循环中都会多出n-1次if判断,就是下面这个:
- if (key.isConnectable()) {
所以,我个人更喜欢***个EchoClient,呵呵,不用注册SelectionKey.OP_CONNECT监听事件。呵呵...
原文链接:http://finux.iteye.com/blog/368955
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