传统的Java 的IO,利用Socket建立服务器,接收客户端连接,一般都是为每一个连接建立一个线程,如果连接数巨大,那么服务器开销也将巨大。。NIO的原理,可以参照图:http://new.51cto.com/files/uploadimg/20080912/150103487.jpg
Socket的Channel在Selector上注册某一种动作,Selector通过select操作,监视所有在该Selector注册过的Channel的对应的动作,如果监测到某一对应的动作,则返回selectedKeys,自己手动取到各个SelectionKey进行相应的处理。当然NIO不仅可以接受Socket的Channel,还有文件操作等其他IO操作。
作业的要求:
使用socket编程实现一个简单的文件服务器。客户端程序实现put功能(将一个文件从本地传到文件服务器)和get功能(从文件服务器取一远程文件存为本地文件)。客户端和文件服务器不在同一台机器上。
put [-h hostname] [-p portname] local_filename remote_filename
get [-h hostname] [-p portname] remote_filename local_filename
服务器端不使用nio,直接使用io的socket代码如下:
- import java.io.*;
- import java.net.ServerSocket;
- import java.net.Socket;
- public class ServerMain {
- public static void main(String[] args) {
- class SocketThread extends Thread{
- private Socket socket;
- private byte[] buf;
- private int len = 0;
- public SocketThread(Socket socket) {
- this.socket = socket;
- buf = new byte[1024];
- }
- @Override
- public void run() {
- try {
- DataInputStream dis = new DataInputStream(socket.getInputStream());
- DataOutputStream dos = new DataOutputStream(socket.getOutputStream());
- //String command = dis.readUTF();
- len = dis.read(buf);
- String command = new String(buf,0,len);
- System.out.println("command=="+command);
- String[] temp =command.split(" ");
- command = temp[0]; //命令 是put还是get
- String filename = temp[1]; //文件名
- File file = new File("C:\\",filename);//假设放在C盘
- if(command.equals("get")){
- if(!file.exists()){
- //dos.writeUTF("notexists");
- dos.write("notexists".getBytes());
- dos.flush();
- System.out.println("没有这个文件,无法提供下载!");
- dis.close();
- dos.close();
- socket.close();
- return;
- }
- //dos.writeUTF("DownloadReady "+file.length());
- dos.write("准备下载".getBytes());
- dos.flush();
- System.out.println("正在接受文件下载...");
- DataInputStream fis = new DataInputStream(new BufferedInputStream(new FileInputStream(file)));
- while ((len = fis.read(buf))!= -1) {
- dos.write(buf, 0, len);
- }
- dos.flush();
- fis.close();
- System.out.println("文件传输完成");
- }
- else {
- //dos.writeUTF("UploadReady");
- dos.write("UploadReady".getBytes());
- dos.flush();
- System.out.println("正在接受文件上传...");
- DataOutputStream fileOut =
- new DataOutputStream(new BufferedOutputStream(new FileOutputStream(file)));
- while ((len = dis.read(buf))!=-1) {
- fileOut.write(buf, 0, len);
- }
- System.out.println("上传完毕!");
- fileOut.close();
- }
- dis.close();
- dos.close();
- socket.close();
- } catch (Exception e) {
- e.printStackTrace();
- }
- }
- }
- System.out.println("等待客户端连接....");
- int index = 0;
- try {
- ServerSocket server = new ServerSocket(9527,300); //端口号9527 允许最大连接数300
- while (true) {
- Socket socket = server.accept();
- System.out.println("收到第"+(++index)+"个连接");
- new SocketThread(socket).start(); //对每个连接创建一个线程
- }
- } catch (Exception e) {
- e.printStackTrace();
- }
- }
- }
使用NIO建立的Socket服务器,代码如下:
- import java.io.BufferedInputStream;
- import java.io.BufferedOutputStream;
- import java.io.DataInputStream;
- import java.io.DataOutputStream;
- import java.io.File;
- import java.io.FileInputStream;
- import java.io.FileOutputStream;
- import java.io.IOException;
- import java.net.InetSocketAddress;
- import java.nio.ByteBuffer;
- import java.nio.CharBuffer;
- 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.nio.charset.CharsetDecoder;
- import java.nio.charset.CharsetEncoder;
- import java.util.Iterator;
- public class NewSocketServer {
- private static final int port = 9527;
- private Selector selector;
- private ByteBuffer clientBuffer = ByteBuffer.allocate(1024);
- private CharsetDecoder decoder = Charset.forName("GB2312").newDecoder();
- private CharsetEncoder encoder = Charset.forName("GB2312").newEncoder();
- //编码解码格式设置成GBK也行.UTF-8不行,中文乱码 (前提都是客户端没有设置任何编码解码格式)
- public void setListener() throws Exception{
- selector = Selector.open(); //打开选择器
- ServerSocketChannel server = ServerSocketChannel.open(); //定义一个 ServerSocketChannel通道
- server.socket().bind(new InetSocketAddress(port)); //ServerSocketChannel绑定端口
- server.configureBlocking(false); //配置通道使用非阻塞模式
- server.register(selector, SelectionKey.OP_ACCEPT); //该通道在selector上注册 接受连接的动作
- while(true)
- {
- selector.select(); //select() 会阻塞,直到在该selector上注册的channel有对应的消息读入
- Iterator iter = selector.selectedKeys().iterator();
- while (iter.hasNext()) {
- SelectionKey key = (SelectionKey) iter.next();
- iter.remove(); // 删除此消息
- process(key); // 当前线程内处理。(为了高效,一般会在另一个线程中处理此消息)
- }
- }
- }
- private void process(SelectionKey key) throws IOException {
- if (key.isAcceptable()) { // 接收请求
- ServerSocketChannel server = (ServerSocketChannel) key.channel();
- SocketChannel channel = server.accept();//类似于io的socket,ServerSocketChannel的accept函数返回 SocketChannel
- channel.configureBlocking(false); //设置非阻塞模式
- SelectionKey sKey = channel.register(selector, SelectionKey.OP_READ);
- sKey.attach("read_command"); //这儿接收到连接请求之后可以为每个连接设置一个ID
- }
- else if (key.isReadable()) { // 读信息
- SocketChannel channel = (SocketChannel) key.channel();
- String name = (String) key.attachment();
- if(name.equals("read_command")){
- int count = channel.read(clientBuffer);
- if (count > 0) {
- clientBuffer.flip();
- CharBuffer charBuffer = decoder.decode(clientBuffer);
- String command = charBuffer.toString();
- //command形如:get abc.png 或者 put aaa.png
- System.out.println("command===="+command); //得到客户端传来的命令
- String[] temp =command.split(" ");
- command = temp[0]; //命令 是put还是get
- String filename = temp[1]; //文件名
- SelectionKey sKey = channel.register(selector,SelectionKey.OP_WRITE);
- if(command.equals("put"))sKey.attach("UploadReady#"+filename); //要保护该通道的文件名
- else if(command.equals("get")){
- if(!new File("C:\\",filename).exists()){ //假设文件都是在C盘根目录
- System.out.println("没有这个文件,无法提供下载!");
- sKey.attach("notexists");
- }
- else sKey.attach("DownloadReady#"+filename); //要保护该通道的文件名
- }
- } else {
- channel.close();
- }
- }
- else if(name.startsWith("read_file")){//这儿可以新开一个线程 文件操作也可以用NIO
- DataOutputStream fileOut =
- new DataOutputStream(
- new BufferedOutputStream(
- new FileOutputStream(
- new File("C:\\",name.split("#")[1]))));
- int passlen = channel.read(clientBuffer);
- while (passlen>=0) {
- clientBuffer.flip();
- fileOut.write(clientBuffer.array(), 0, passlen);
- passlen = channel.read(clientBuffer);
- }
- System.out.println("上传完毕!");
- fileOut.close();
- channel.close();
- }
- clientBuffer.clear();
- }
- else if (key.isWritable()) { // 写事件
- SocketChannel channel = (SocketChannel) key.channel();
- String flag = (String) key.attachment();
- if(flag.startsWith("downloading")){//这儿可以新开一个线程 文件操作也可以用NIO
- DataInputStream fis = new DataInputStream(
- new BufferedInputStream(
- new FileInputStream(
- new File("C:\\",flag.split("#")[1]))));
- byte[] buf = new byte[1024];
- int len =0;
- while ((len = fis.read(buf))!= -1) {
- channel.write(ByteBuffer.wrap(buf, 0, len));
- }
- fis.close();
- System.out.println("文件传输完成");
- channel.close();
- }
- else if(flag.equals("notexists")){
- //channel.write(encoder.encode(CharBuffer.wrap(flag)));
- channel.write(ByteBuffer.wrap(flag.getBytes())); //不用编码也行 客户端直接接收 中文也不是乱码
- channel.close();
- }
- else if(flag.startsWith("UploadReady")){
- channel.write(encoder.encode(CharBuffer.wrap("UploadReady")));
- //这儿如果不重新注册该通道的读操作 selector选择到该通道的将继续永远是写操作,也就无法跳转到上面的接受上传的处理
- SelectionKey sKey =channel.register(selector, SelectionKey.OP_READ);//register是覆盖的????!!!
- sKey.attach("read_file#"+flag.split("#")[1]);
- //key.attach("read_file#"+flag.split("#")[1]); //select不到读操作
- }
- else if(flag.startsWith("DownloadReady")){
- channel.write(ByteBuffer.wrap("准备下载".getBytes()));
- //channel.write(encoder.encode(CharBuffer.wrap("准备下载")));
- key.attach("downloading#"+flag.split("#")[1]);
- }
- }
- }
- public static void main(String[] args) {
- try {
- System.out.println("等待来至" + port + "端口的客户端连接.....");
- new NewSocketServer().setListener();
- } catch (Exception e) {
- e.printStackTrace();
- }
- }
- }
客户端代码如下:
- import java.io.*;
- import java.net.InetAddress;
- import java.net.Socket;
- import java.util.Scanner;
- public class ClientMain {
- private int ServerPort = 9527;
- private String ServerAddress = "192.168.1.154";
- private String GetOrPut = "get";
- private String local_filename = "";
- private String remote_filename = "";
- private byte[] buf;
- private int len;
- class SocketThread extends Thread{
- @Override
- public void run() {
- try {
- File file = new File("C:\\",local_filename); //假设文件放在C盘
- if(!file.exists()&&GetOrPut.equals("put")){
- System.out.println("本地没有这个文件,无法上传!");
- return;
- }
- InetAddress loalhost = InetAddress.getLocalHost();
- Socket socket = new Socket(ServerAddress,ServerPort,loalhost,44);
- //服务器IP地址 端口号 本机IP 本机端口号
- DataInputStream dis = new DataInputStream(socket.getInputStream());
- DataOutputStream dos = new DataOutputStream(socket.getOutputStream());
- //dos.writeUTF(GetOrPut+" "+remote_filename);//服务器端如果是io的socket,writeUTF和writeUTF对接
- dos.write((GetOrPut+" "+remote_filename).getBytes());
- dos.flush();
- //String tempString = dis.writeUTF();
- buf = new byte[1024];
- len = dis.read(buf);
- String tempString = new String(buf,0,len);//服务器反馈的信息
- //System.out.println(tempString);
- if(tempString.equals("notexists")){
- System.out.println("服务器没有这个文件,无法下载!");
- dos.close();
- dis.close();
- socket.close();
- return;
- }
- if(tempString.startsWith("准备下载")){
- DataOutputStream fileOut =
- new DataOutputStream(new BufferedOutputStream(new FileOutputStream(file)));
- while ((len = dis.read(buf))!=-1) {
- fileOut.write(buf, 0, len);
- }
- System.out.println("下载完毕!");
- fileOut.close();
- dos.close();
- dis.close();
- socket.close();
- }
- else if(tempString.equals("UploadReady")){
- System.out.println("正在上传文件.......");
- DataInputStream fis = new DataInputStream(new BufferedInputStream(new FileInputStream(file)));
- while ((len = fis.read(buf))!= -1) {
- dos.write(buf, 0, len);
- }
- dos.flush();
- System.out.println("上传完毕!");
- fis.close();
- dis.close();
- dos.close();
- socket.close();
- }
- } catch (Exception e) {
- e.printStackTrace();
- }
- }
- }
- public boolean checkCommand(String command)
- {
- if(!command.startsWith("put")&&!command.startsWith("get")){
- System.out.println("输入命令错误");
- return false;
- }
- int index = -1;
- String temp = "";
- String[] tempStrings = null;
- if((index=command.indexOf("-h"))>0){
- temp = command.substring(index+3);
- temp = temp.substring(0, temp.indexOf(' '));
- ServerAddress = temp;
- }
- if((index=command.indexOf("-p"))>0){
- temp = command.substring(index+3);
- temp = temp.substring(0, temp.indexOf(' '));
- ServerPort = Integer.valueOf(temp);
- }
- tempStrings = command.split(" ");
- if(command.startsWith("put")){
- GetOrPut = "put";
- local_filename = tempStrings[tempStrings.length-2];
- remote_filename = tempStrings[tempStrings.length-1];
- }
- else if(command.startsWith("get")){
- GetOrPut = "get";
- local_filename = tempStrings[tempStrings.length-1];
- remote_filename = tempStrings[tempStrings.length-2];
- }
- return true;
- }
- public static void main(String[] args) {
- ClientMain thisC= new ClientMain();
- Scanner sc = new Scanner(System.in);
- String commandString = "";
- do {
- System.out.println("请输入命令:");
- commandString = sc.nextLine();
- } while (!thisC.checkCommand(commandString));
- ClientMain.SocketThread a = thisC.new SocketThread();
- a.start();
- }
- }
评论
- int count = channel.read(clientBuffer);
- if (count > 0) {
- //命令解释
- }
channel.read(clientBuffer) 有可能接收到命令字节的一部分,命令解释会出问题
用nio写的server这段。
while (passlen>=0) {
clientBuffer.flip();
fileOut.write(clientBuffer.array(), 0, passlen);
passlen = channel.read(clientBuffer);
}
应嘎是这样的逻辑:
while (passlen>=0) {
if(passlen!=0) {
clientBuffer.flip();
}
fileOut.write(clientBuffer.array(), 0, passlen);
passlen = channel.read(clientBuffer);
}
这样传大文件也不都会错了。