如何利用NIO建立Socket服务器

本篇内容介绍了“如何利用NIO建立Socket服务器”的有关知识，在实际案例的操作过程中，不少人都会遇到这样的困境，接下来就让小编带领大家学习一下如何处理这些情况吧！希望大家仔细阅读，能够学有所成！

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：

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_filenameget [-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***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();     } }

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