• 利用NIO建立Socket服务器

    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。

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    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_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：

    1. import java.io.*; 
    2. import java.net.ServerSocket; 
    3. import java.net.Socket; 
    4.  
    5. public class ServerMain { 
    6.      
    7.     public static void main(String[] args) { 
    8.  
    9.         class SocketThread extends Thread{ 
    10.              
    11.             private Socket socket; 
    12.             private byte[] buf; 
    13.             private int len = 0; 
    14.             public SocketThread(Socket socket) {  
    15.                 this.socket = socket; 
    16.                 buf = new byte[1024]; 
    17.             } 
    18.  
    19.             @Override 
    20.             public void run() { 
    21.                 try {    
    22.                     DataInputStream dis = new DataInputStream(socket.getInputStream()); 
    23.                     DataOutputStream dos = new DataOutputStream(socket.getOutputStream());  
    24.                      
    25.                     //String command = dis.readUTF();  
    26.                     len = dis.read(buf); 
    27.                     String command = new String(buf,0,len); 
    28.                      
    29.                     System.out.println("command=="+command); 
    30.                      
    31.                     String[] temp =command.split(" "); 
    32.                     command = temp[0];  //命令  是put还是get 
    33.                     String filename = temp[1];  //文件名 
    34.                      
    35.                     File file = new File("C:\",filename);//假设放在C盘 
    36.                     if(command.equals("get")){ 
    37.                         if(!file.exists()){ 
    38.                             //dos.writeUTF("notexists"); 
    39.                             dos.write("notexists".getBytes()); 
    40.                             dos.flush(); 
    41.                             System.out.println("没有这个文件，无法提供下载！"); 
    42.                             dis.close(); 
    43.                             dos.close(); 
    44.                             socket.close(); 
    45.                             return; 
    46.                         } 
    47.                         //dos.writeUTF("DownloadReady "+file.length());  
    48.                         dos.write("准备下载".getBytes()); 
    49.                         dos.flush(); 
    50.                          
    51.                         System.out.println("正在接受文件下载..."); 
    52.                         DataInputStream fis = new DataInputStream(new BufferedInputStream(new FileInputStream(file)));  
    53.    
    54.                         while ((len = fis.read(buf))!= -1) {  
    55.                             dos.write(buf, 0, len); 
    56.                         } 
    57.                         dos.flush(); 
    58.                          
    59.                         fis.close();      
    60.                         System.out.println("文件传输完成"); 
    61.                     } 
    62.                     else {  
    63.                         //dos.writeUTF("UploadReady");  
    64.                         dos.write("UploadReady".getBytes()); 
    65.                         dos.flush(); 
    66.                          
    67.                         System.out.println("正在接受文件上传..."); 
    68.                         DataOutputStream fileOut =  
    69.                             new DataOutputStream(new BufferedOutputStream(new FileOutputStream(file))); 
    70.   
    71.                         while ((len = dis.read(buf))!=-1) {    
    72.                             fileOut.write(buf, 0, len); 
    73.                         } 
    74.                         System.out.println("上传完毕！"); 
    75.                         fileOut.close();  
    76.                     } 
    77.                     dis.close(); 
    78.                     dos.close(); 
    79.                     socket.close();  
    80.                 } catch (Exception e) { 
    81.                     e.printStackTrace(); 
    82.                 } 
    83.             } 
    84.              
    85.         } 
    86.          
    87.         System.out.println("等待客户端连接...."); 
    88.         int index = 0; 
    89.         try { 
    90.             ServerSocket server = new ServerSocket(9527,300); //端口号9527  允许最大连接数300 
    91.             while (true) { 
    92.                 Socket socket = server.accept(); 
    93.                 System.out.println("收到第"+(++index)+"个连接"); 
    94.                 new SocketThread(socket).start(); //对每个连接创建一个线程 
    95.             } 
    96.         } catch (Exception e) { 
    97.             e.printStackTrace(); 
    98.         } 
    99.     } 
    100. } 

    使用NIO建立的Socket服务器，代码如下：

    1. import java.io.BufferedInputStream; 
    2. import java.io.BufferedOutputStream; 
    3. import java.io.DataInputStream; 
    4. import java.io.DataOutputStream; 
    5. import java.io.File; 
    6. import java.io.FileInputStream; 
    7. import java.io.FileOutputStream; 
    8. import java.io.IOException; 
    9. import java.net.InetSocketAddress; 
    10. import java.nio.ByteBuffer;  
    11. import java.nio.CharBuffer; 
    12. import java.nio.channels.SelectionKey; 
    13. import java.nio.channels.Selector; 
    14. import java.nio.channels.ServerSocketChannel; 
    15. import java.nio.channels.SocketChannel; 
    16. import java.nio.charset.Charset; 
    17. import java.nio.charset.CharsetDecoder; 
    18. import java.nio.charset.CharsetEncoder; 
    19. import java.util.Iterator; 
    20.  
    21. public class NewSocketServer { 
    22.   
    23.     private static final int port = 9527; 
    24.     private Selector selector; 
    25.     private ByteBuffer clientBuffer = ByteBuffer.allocate(1024);   
    26.     private CharsetDecoder decoder = Charset.forName("GB2312").newDecoder(); 
    27.     private CharsetEncoder encoder = Charset.forName("GB2312").newEncoder();  
    28.     //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） 
    29.      
    30.     public void setListener() throws Exception{ 
    31.          
    32.         selector = Selector.open(); //打开选择器    
    33.          
    34.         ServerSocketChannel server = ServerSocketChannel.open();  //定义一个 ServerSocketChannel通道 
    35.         server.socket().bind(new InetSocketAddress(port));  //ServerSocketChannel绑定端口   
    36.         server.configureBlocking(false);   //配置通道使用非阻塞模式 
    37.         server.register(selector, SelectionKey.OP_ACCEPT); //该通道在selector上注册  接受连接的动作 
    38.          
    39.         while(true) 
    40.         {     
    41.             selector.select();   //select() 会阻塞，直到在该selector上注册的channel有对应的消息读入 
    42.             Iterator iter = selector.selectedKeys().iterator();    
    43.             while (iter.hasNext()) {     
    44.                 SelectionKey key = (SelectionKey) iter.next();    
    45.                 iter.remove();  // 删除此消息  
    46.                 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） 
    47.             }    
    48.         }    
    49.     } 
    50.      
    51.      private void process(SelectionKey key) throws IOException {    
    52.             if (key.isAcceptable()) { // 接收请求    
    53.                 ServerSocketChannel server = (ServerSocketChannel) key.channel();    
    54.                 SocketChannel channel = server.accept();//类似于io的socket，ServerSocketChannel的accept函数返回 SocketChannel 
    55.                 channel.configureBlocking(false);   //设置非阻塞模式    
    56.                 SelectionKey sKey = channel.register(selector, SelectionKey.OP_READ);  
    57.                 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 
    58.             }  
    59.             else if (key.isReadable()) { // 读信息     
    60.                 SocketChannel channel = (SocketChannel) key.channel();    
    61.                 String name = (String) key.attachment();  
    62.                 if(name.equals("read_command")){ 
    63.                     int count = channel.read(clientBuffer);  
    64.                     if (count > 0) {    
    65.                         clientBuffer.flip();    
    66.                         CharBuffer charBuffer = decoder.decode(clientBuffer);    
    67.                         String command = charBuffer.toString();    
    68.                          
    69.                         //command形如：get abc.png 或者  put aaa.png 
    70.                         System.out.println("command===="+command);  //得到客户端传来的命令  
    71.                          
    72.                         String[] temp =command.split(" "); 
    73.                         command = temp[0];  //命令  是put还是get 
    74.                         String filename = temp[1];  //文件名 
    75.                          
    76.                         SelectionKey sKey = channel.register(selector,SelectionKey.OP_WRITE);    
    77.                         if(command.equals("put"))sKey.attach("UploadReady#"+filename);  //要保护该通道的文件名 
    78.                         else if(command.equals("get")){  
    79.                             if(!new File("C:\",filename).exists()){ //假设文件都是在C盘根目录 
    80.                                 System.out.println("没有这个文件，无法提供下载！"); 
    81.                                 sKey.attach("notexists");  
    82.                             } 
    83.                             else sKey.attach("DownloadReady#"+filename); //要保护该通道的文件名 
    84.                         } 
    85.                     } else {    
    86.                         channel.close();    
    87.                     }    
    88.                 } 
    89.                 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  
    90.                     DataOutputStream fileOut =  
    91.                         new DataOutputStream( 
    92.                                 new BufferedOutputStream( 
    93.                                         new FileOutputStream( 
    94.                                                 new File("C:\",name.split("#")[1])))); 
    95.   
    96.                     int passlen = channel.read(clientBuffer);   
    97.                     while (passlen>=0) {    
    98.                         clientBuffer.flip();   
    99.                         fileOut.write(clientBuffer.array(), 0, passlen);  
    100.                         passlen = channel.read(clientBuffer); 
    101.                     } 
    102.                     System.out.println("上传完毕！"); 
    103.                     fileOut.close();  
    104.                     channel.close(); 
    105.                 } 
    106.                 clientBuffer.clear();    
    107.             }  
    108.             else if (key.isWritable()) { // 写事件    
    109.                 SocketChannel channel = (SocketChannel) key.channel();    
    110.                 String flag = (String) key.attachment();     
    111.                 if(flag.startsWith("downloading")){//这儿可以新开一个线程   文件操作也可以用NIO 
    112.                     DataInputStream fis = new DataInputStream( 
    113.                             new BufferedInputStream( 
    114.                                     new FileInputStream( 
    115.                                             new File("C:\",flag.split("#")[1]))));  
    116.                       
    117.                     byte[] buf = new byte[1024]; 
    118.                     int len =0;  
    119.                     while ((len = fis.read(buf))!= -1) {  
    120.                         channel.write(ByteBuffer.wrap(buf, 0, len));   
    121.                     }   
    122.                     fis.close();      
    123.                     System.out.println("文件传输完成"); 
    124.                     channel.close(); 
    125.                 } 
    126.                 else if(flag.equals("notexists")){  
    127.                     //channel.write(encoder.encode(CharBuffer.wrap(flag)));    
    128.                     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 
    129.                     channel.close(); 
    130.                 } 
    131.                 else if(flag.startsWith("UploadReady")){  
    132.                     channel.write(encoder.encode(CharBuffer.wrap("UploadReady")));  
    133.                      
    134.                     //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 
    135.                     SelectionKey sKey =channel.register(selector, SelectionKey.OP_READ);//register是覆盖的????!!! 
    136.                     sKey.attach("read_file#"+flag.split("#")[1]); 
    137.                     //key.attach("read_file#"+flag.split("#")[1]); //select不到读操作 
    138.                 } 
    139.                 else if(flag.startsWith("DownloadReady")){  
    140.                     channel.write(ByteBuffer.wrap("准备下载".getBytes()));  
    141.                     //channel.write(encoder.encode(CharBuffer.wrap("准备下载")));    
    142.                     key.attach("downloading#"+flag.split("#")[1]); 
    143.                 }  
    144.             }   
    145.         }    
    146.      
    147.     public static void main(String[] args) { 
    148.          
    149.         try { 
    150.              System.out.println("等待来至" + port + "端口的客户端连接.....");  
    151.             new NewSocketServer().setListener(); 
    152.         } catch (Exception e) { 
    153.             e.printStackTrace(); 
    154.         } 
    155.  
    156.     } 
    157. } 

    客户端代码如下：

    1. import java.io.*; 
    2. import java.net.InetAddress; 
    3. import java.net.Socket; 
    4. import java.util.Scanner; 
    5.  
    6. public class ClientMain { 
    7.  
    8.     private   int ServerPort = 9527; 
    9.     private   String ServerAddress = "192.168.1.154"; 
    10.     private   String GetOrPut = "get";    
    11.     private   String local_filename = "";  
    12.     private   String remote_filename  = "";  
    13.     private   byte[] buf; 
    14.     private   int len; 
    15.     class SocketThread extends Thread{ 
    16.          
    17.         @Override 
    18.         public void run() { 
    19.              try { 
    20.                  
    21.                 File file = new File("C:\",local_filename); //假设文件放在C盘 
    22.                 if(!file.exists()&&GetOrPut.equals("put")){  
    23.                     System.out.println("本地没有这个文件，无法上传！");  
    24.                     return; 
    25.                 }  
    26.                  
    27.                 InetAddress loalhost = InetAddress.getLocalHost(); 
    28.                 Socket socket = new Socket(ServerAddress,ServerPort,loalhost,44); 
    29.                                             //服务器IP地址  端口号   本机IP 本机端口号 
    30.                 DataInputStream dis = new DataInputStream(socket.getInputStream()); 
    31.                 DataOutputStream dos = new DataOutputStream(socket.getOutputStream()); 
    32.                   
    33.                 //dos.writeUTF(GetOrPut+" "+remote_filename);//服务器端如果是io的socket，writeUTF和writeUTF对接 
    34.                 dos.write((GetOrPut+" "+remote_filename).getBytes()); 
    35.                 dos.flush();  
    36.                
    37.                 //String tempString = dis.writeUTF();  
    38.                 buf = new byte[1024]; 
    39.                 len = dis.read(buf); 
    40.                 String tempString = new String(buf,0,len);//服务器反馈的信息 
    41.                  
    42.                 //System.out.println(tempString);  
    43.                 if(tempString.equals("notexists")){ 
    44.                     System.out.println("服务器没有这个文件，无法下载！");  
    45.                     dos.close(); 
    46.                     dis.close(); 
    47.                     socket.close(); 
    48.                     return; 
    49.                 } 
    50.                  
    51.                 if(tempString.startsWith("准备下载")){   
    52.                     DataOutputStream fileOut =  
    53.                         new DataOutputStream(new BufferedOutputStream(new FileOutputStream(file))); 
    54.   
    55.                     while ((len = dis.read(buf))!=-1) {    
    56.                         fileOut.write(buf, 0, len); 
    57.                     } 
    58.                     System.out.println("下载完毕！"); 
    59.                     fileOut.close(); 
    60.                     dos.close(); 
    61.                     dis.close(); 
    62.                     socket.close(); 
    63.                 } 
    64.                 else if(tempString.equals("UploadReady")){   
    65.                     System.out.println("正在上传文件......."); 
    66.                     DataInputStream fis = new DataInputStream(new BufferedInputStream(new FileInputStream(file)));  
    67.                        
    68.                     while ((len = fis.read(buf))!= -1) {   
    69.                         dos.write(buf, 0, len); 
    70.                     } 
    71.                     dos.flush(); 
    72.                     System.out.println("上传完毕！"); 
    73.                     fis.close(); 
    74.                     dis.close(); 
    75.                     dos.close(); 
    76.                     socket.close(); 
    77.                 } 
    78.                  
    79.             } catch (Exception e) { 
    80.                 e.printStackTrace(); 
    81.             } 
    82.         } 
    83.          
    84.     } 
    85.      
    86.     public boolean checkCommand(String command) 
    87.     {  
    88.         if(!command.startsWith("put")&&!command.startsWith("get")){ 
    89.             System.out.println("输入命令错误"); 
    90.             return false; 
    91.         } 
    92.          
    93.         int index = -1; 
    94.         String temp = ""; 
    95.         String[] tempStrings = null; 
    96.          
    97.         if((index=command.indexOf("-h"))>0){ 
    98.             temp = command.substring(index+3); 
    99.             temp = temp.substring(0, temp.indexOf(' ')); 
    100.             ServerAddress = temp; 
    101.         } 
    102.         if((index=command.indexOf("-p"))>0){ 
    103.             temp = command.substring(index+3); 
    104.             temp = temp.substring(0, temp.indexOf(' ')); 
    105.             ServerPort = Integer.valueOf(temp); 
    106.         } 
    107.          
    108.         tempStrings = command.split(" "); 
    109.         if(command.startsWith("put")){ 
    110.             GetOrPut = "put"; 
    111.             local_filename = tempStrings[tempStrings.length-2]; 
    112.             remote_filename = tempStrings[tempStrings.length-1]; 
    113.         } 
    114.         else if(command.startsWith("get")){ 
    115.             GetOrPut = "get"; 
    116.             local_filename = tempStrings[tempStrings.length-1]; 
    117.             remote_filename = tempStrings[tempStrings.length-2]; 
    118.         } 
    119.          
    120.         return true; 
    121.     } 
    122.      
    123.     public static void main(String[] args) { 
    124.         ClientMain thisC= new ClientMain();  
    125.         Scanner sc = new Scanner(System.in); 
    126.         String commandString = ""; 
    127.         do { 
    128.             System.out.println("请输入命令：");  
    129.             commandString = sc.nextLine(); 
    130.         } while (!thisC.checkCommand(commandString));  
    131.          
    132.         ClientMain.SocketThread a = thisC.new SocketThread(); 
    133.         a.start(); 
    134.     } 
    135. } 

    原文链接：http://tonl.iteye.com/blog/1202817
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  • 原文地址：https://www.cnblogs.com/wnlja/p/4368640.html
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