SocketChannel 例子(转)

Socket通信比较常见的问题有如下几种：
1、设置收发超时；
2、正确的每一个bit的收发；
3、物理线路故障的保护；
4、始终能正常工作；
5、尽量少占系统资源；
n、……
而Socket编程有一个共性，尽管100个人可能会写出1000种实现，但做的事情却只有一种，就是：通信。
为此，通过学习dnsjava的通信代码，加上自己在一些项目中的实践，现在给出TCP通信的例子实现如下，希望能够给想偷懒的人一个简单的解决方案。
本方案在正常的局域网连接中测试过几百万次没什么问题。缺乏更艰苦的环境，所以如果使用这些代码发生任何风险的话……
（TcpChannel代码为Brian Wellington所做，原名为TCPClient，经本人稍作改动）

Java代码

1. // Copyright (c) 2005 Brian Wellington (bwelling@xbill.org)  
2.   
3. package asynchronizedchannel;  
4.   
5. import java.io.*;  
6. import java.net.*;  
7. import java.nio.*;  
8. import java.nio.channels.*;  
9.   
10. final class TcpChannel  
11. {  
12.     private long endTime;  
13.     private SelectionKey key;  
14.   
15.     public TcpChannel(SelectableChannel channel, long endTime, int op) throws IOException  
16.     {  
17.         boolean done = false;  
18.         Selector selector = null;  
19.         this.endTime = endTime;  
20.         try {  
21.             selector = Selector.open();  
22.             channel.configureBlocking(false);  
23.             key = channel.register(selector, op);  
24.             done = true;  
25.         } finally {  
26.             if (!done && selector != null) {  
27.                 selector.close();  
28.             }  
29.             if (!done) {  
30.                 channel.close();  
31.             }  
32.         }  
33.     }  
34.   
35.     static void blockUntil(SelectionKey key, long endTime) throws IOException  
36.     {  
37.         long timeout = endTime - System.currentTimeMillis();  
38.         int nkeys = 0;  
39.         if (timeout > 0) {  
40.             nkeys = key.selector().select(timeout);  
41.         } else if (timeout == 0) {  
42.             nkeys = key.selector().selectNow();  
43.         }  
44.         if (nkeys == 0) {  
45.             throw new SocketTimeoutException();  
46.         }  
47.     }  
48.   
49.     void cleanup()  
50.     {  
51.         try {  
52.             key.selector().close();  
53.             key.channel().close();  
54.         } catch (IOException ex) {  
55.             ex.printStackTrace();  
56.         }  
57.     }  
58.   
59.     void bind(SocketAddress addr) throws IOException  
60.     {  
61.         SocketChannel channel = (SocketChannel) key.channel();  
62.         channel.socket().bind(addr);  
63.     }  
64.   
65.     void connect(SocketAddress addr) throws IOException  
66.     {  
67.         SocketChannel channel = (SocketChannel) key.channel();  
68.         if (channel.connect(addr))  
69.             return;  
70.         key.interestOps(SelectionKey.OP_CONNECT);  
71.         try {  
72.             while (!channel.finishConnect()) {  
73.                 if (!key.isConnectable()) {  
74.                     blockUntil(key, endTime);  
75.                 }  
76.             }  
77.         } finally {  
78.             if (key.isValid()) {  
79.                 key.interestOps(0);  
80.             }  
81.         }  
82.     }  
83.   
84.     void send(ByteBuffer buffer) throws IOException  
85.     {  
86.         Send.operate(key, buffer, endTime);  
87.     }  
88.   
89.     void recv(ByteBuffer buffer) throws IOException  
90.     {  
91.         Recv.operate(key, buffer, endTime);  
92.     }  
93. }  
94.   
95. interface Operator  
96. {  
97.     class Operation  
98.     {  
99.         static void operate(final int op, final SelectionKey key, final ByteBuffer buffer, final long endTime, final Operator optr) throws IOException  
100.         {  
101.             final SocketChannel channel = (SocketChannel) key.channel();  
102.             final int total = buffer.capacity();  
103.             key.interestOps(op);  
104.             try {  
105.                 while (buffer.position() < total) {  
106.                     if (System.currentTimeMillis() > endTime) {  
107.                         throw new SocketTimeoutException();  
108.                     }  
109.                     if ((key.readyOps() & op) != 0) {  
110.                         if (optr.io(channel, buffer) < 0) {  
111.                             throw new EOFException();  
112.                         }  
113.                     } else {  
114.                         TcpChannel.blockUntil(key, endTime);  
115.                     }  
116.                 }  
117.             } finally {  
118.                 if (key.isValid()) {  
119.                     key.interestOps(0);  
120.                 }  
121.             }  
122.         }  
123.     }  
124.   
125.     int io(SocketChannel channel, ByteBuffer buffer) throws IOException;  
126. }  
127. class Send implements Operator  
128. {  
129.     public int io(SocketChannel channel, ByteBuffer buffer) throws IOException  
130.     {  
131.         return channel.write(buffer);  
132.     }  
133.     public static final void operate(final SelectionKey key, final ByteBuffer buffer, final long endTime) throws IOException  
134.     {  
135.         Operation.operate(SelectionKey.OP_WRITE, key, buffer, endTime, operator);  
136.     }  
137.     public static final Send operator = new Send();  
138. }  
139.   
140. class Recv implements Operator  
141. {  
142.     public int io(SocketChannel channel, ByteBuffer buffer) throws IOException  
143.     {  
144.         return channel.read(buffer);  
145.     }  
146.       
147.     public static final void operate(final SelectionKey key, final ByteBuffer buffer, final long endTime) throws IOException  
148.     {  
149.         Operation.operate(SelectionKey.OP_READ, key, buffer, endTime, operator);  
150.     }  
151.     public static final Recv operator = new Recv();  
152. }  

// Copyright (c) 2005 Brian Wellington (bwelling@xbill.org)  package asynchronizedchannel;  import java.io.*; import java.net.*; import java.nio.*; import java.nio.channels.*;  final class TcpChannel {     private long endTime;     private SelectionKey key;      public TcpChannel(SelectableChannel channel, long endTime, int op) throws IOException     {         boolean done = false;         Selector selector = null;         this.endTime = endTime;         try {             selector = Selector.open();             channel.configureBlocking(false);             key = channel.register(selector, op);             done = true;         } finally {             if (!done && selector != null) {                 selector.close();             }             if (!done) {                 channel.close();             }         }     }      static void blockUntil(SelectionKey key, long endTime) throws IOException     {         long timeout = endTime - System.currentTimeMillis();         int nkeys = 0;         if (timeout > 0) {             nkeys = key.selector().select(timeout);         } else if (timeout == 0) {             nkeys = key.selector().selectNow();         }         if (nkeys == 0) {             throw new SocketTimeoutException();         }     }      void cleanup()     {         try {             key.selector().close();             key.channel().close();         } catch (IOException ex) {             ex.printStackTrace();         }     }      void bind(SocketAddress addr) throws IOException     {         SocketChannel channel = (SocketChannel) key.channel();         channel.socket().bind(addr);     }      void connect(SocketAddress addr) throws IOException     {         SocketChannel channel = (SocketChannel) key.channel();         if (channel.connect(addr))             return;         key.interestOps(SelectionKey.OP_CONNECT);         try {             while (!channel.finishConnect()) {                 if (!key.isConnectable()) {                     blockUntil(key, endTime);                 }             }         } finally {             if (key.isValid()) {                 key.interestOps(0);             }         }     }      void send(ByteBuffer buffer) throws IOException     {         Send.operate(key, buffer, endTime);     }      void recv(ByteBuffer buffer) throws IOException     {         Recv.operate(key, buffer, endTime);     } }  interface Operator {     class Operation     {         static void operate(final int op, final SelectionKey key, final ByteBuffer buffer, final long endTime, final Operator optr) throws IOException         {             final SocketChannel channel = (SocketChannel) key.channel();             final int total = buffer.capacity();             key.interestOps(op);             try {                 while (buffer.position() < total) {                     if (System.currentTimeMillis() > endTime) {                         throw new SocketTimeoutException();                     }                     if ((key.readyOps() & op) != 0) {                         if (optr.io(channel, buffer) < 0) {                             throw new EOFException();                         }                     } else {                         TcpChannel.blockUntil(key, endTime);                     }                 }             } finally {                 if (key.isValid()) {                     key.interestOps(0);                 }             }         }     }      int io(SocketChannel channel, ByteBuffer buffer) throws IOException; } class Send implements Operator {     public int io(SocketChannel channel, ByteBuffer buffer) throws IOException     {         return channel.write(buffer);     }     public static final void operate(final SelectionKey key, final ByteBuffer buffer, final long endTime) throws IOException     {         Operation.operate(SelectionKey.OP_WRITE, key, buffer, endTime, operator);     }     public static final Send operator = new Send(); }  class Recv implements Operator {     public int io(SocketChannel channel, ByteBuffer buffer) throws IOException     {         return channel.read(buffer);     }          public static final void operate(final SelectionKey key, final ByteBuffer buffer, final long endTime) throws IOException     {         Operation.operate(SelectionKey.OP_READ, key, buffer, endTime, operator);     }     public static final Recv operator = new Recv(); } 

使用演示见以下代码。
大致说明一下，Server端开5656侦听，Client端开若干线程测试Socket通信。每次发送240字节信息+16字节MD5校验。服务端收到信息之后做MD5检查，正确的，发送“.xxxx”表示认可，否则发送“?xxxx”表示故障。
正式应用中可以再设置tryout尝试n次。
Server端，代码演示：

Java代码

1. package asynchronizedchannel;  
2.   
3. import java.io.IOException;  
4. import java.net.InetSocketAddress;  
5. import java.nio.ByteBuffer;  
6. import java.nio.channels.SelectionKey;  
7. import java.nio.channels.Selector;  
8. import java.nio.channels.ServerSocketChannel;  
9. import java.nio.channels.SocketChannel;  
10. import java.security.MessageDigest;  
11. import java.util.Iterator;  
12.   
13. public class Server  
14. {  
15.   
16.     /** 
17.      * 服务端通信范例程序主函数 
18.      *  
19.      * @param args 
20.      * @throws IOException 
21.      */  
22.     public static void main(String[] args) throws IOException  
23.     {  
24.         // Create the selector  
25.         final Selector selector = Selector.open();  
26.         final ServerSocketChannel server = ServerSocketChannel.open();  
27.         server.configureBlocking(false);  
28.         server.socket().bind(new InetSocketAddress("xx.xx.xx.xx", 5656), 5);  
29.         // Register both channels with selector  
30.         server.register(selector, SelectionKey.OP_ACCEPT);  
31.         new Thread(new Daemon(selector)).start();  
32.     }  
33. }  
34.   
35. class Daemon implements Runnable  
36. {  
37.     private final Selector selector;  
38.   
39.     Daemon(Selector selector)  
40.     {  
41.         this.selector = selector;  
42.     }  
43.   
44.     public void run()  
45.     {  
46.         while (true) {  
47.             try {  
48.                 // Wait for an event  
49.                 selector.select();  
50.   
51.                 // Get list of selection keys with pending events  
52.                 Iterator<SelectionKey> it = selector.selectedKeys().iterator();  
53.   
54.                 // Process each key  
55.                 while (it.hasNext()) {  
56.                     // Get the selection key  
57.                     SelectionKey selKey = it.next();  
58.   
59.                     // Remove it from the list to indicate that it is being processed  
60.                     it.remove();  
61.   
62.                     // Check if it's a connection request  
63.                     if (selKey.isAcceptable()) {  
64.                         // Get channel with connection request  
65.                         ServerSocketChannel server = (ServerSocketChannel) selKey.channel();  
66.                         // Accept the connection request.  
67.                         // If serverSocketChannel is blocking, this method blocks.  
68.                         // The returned channel is in blocking mode.  
69.                         SocketChannel channel = server.accept();  
70.   
71.                         // If serverSocketChannel is non-blocking, sChannel may be null  
72.                         if (channel != null) {  
73.                             // Use the socket channel to communicate with the client  
74.                             new Thread(new ServerHandler(channel)).start();  
75.                         } else {  
76.                             System.out.println("---No Connection---");  
77.                             // There were no pending connection requests; try again later.  
78.                             // To be notified of connection requests,  
79.                         }  
80.                     }  
81.                 }  
82.             } catch (Exception ex) {  
83.                 ex.printStackTrace();  
84.             }  
85.         }  
86.     }  
87. }  
88.   
89. class ServerHandler implements Runnable  
90. {  
91.     private static final long timeout = 30 * 1000; // 设置超时时间为30秒  
92.     private static int counter = 0;  
93.     private final TcpChannel channel;  
94.     private final MessageDigest md;  
95.   
96.     ServerHandler(SocketChannel channel) throws Exception  
97.     {  
98.         this.channel = new TcpChannel(channel, System.currentTimeMillis() + timeout, SelectionKey.OP_READ);  
99.         md = MessageDigest.getInstance("md5");  
100.     }  
101.   
102.     public void run()  
103.     {  
104.         try {  
105.             while (true) {  
106.                 work();  
107.                 synchronized (ServerHandler.class) {  
108.                     if ((++counter & 65535) == 0) {  
109.                         System.out.println(counter);  
110.                     }  
111.                 }  
112.             }  
113.         } catch (Exception e) {  
114.             e.printStackTrace();  
115.         } finally {  
116.             channel.cleanup();  
117.         }  
118.     }  
119.   
120.     private void work() throws IOException  
121.     { // 模拟工作流程  
122.         byte[] cache = new byte[256], reply = new byte[5];  
123.         read(cache, reply);  
124.     }  
125.   
126.     private void read(byte[] cache, byte[] reply) throws IOException  
127.     { // 从套接字读入数据  
128.         channel.recv(ByteBuffer.wrap(cache));  
129.         md.reset();  
130.         md.update(cache, 0, 240);  
131.         byte[] md5 = md.digest(); // 使用前240字节产生MD5校验码  
132.         if (!ExtArrays.partialEquals(md5, 0, cache, 240, 16)) { // 与后16字节比较  
133.             reply[0] = '?';  
134.             System.out.println("MISMATCH!");  
135.         } else {  
136.             reply[0] = '.';  
137.         }  
138.         channel.send(ByteBuffer.wrap(reply)); // 返回接收结果  
139.     }  
140. }  
141.   
142. final class ExtArrays  
143. {  
144.     private ExtArrays()  
145.     {  
146.     }  
147.   
148.     public static boolean partialEquals(byte[] a, int offset_a, byte[] b, int offset_b, int len)  
149.     { // 字节数组的部分比较  
150.         if (a == null || b == null) {  
151.             return false;  
152.         }  
153.         if (offset_a + len > a.length || offset_b + len > b.length) {  
154.             return false;  
155.         }  
156.         for (int i = offset_a, j = offset_b, k = len; k > 0; i++, j++, k--) {  
157.             if (a[i] != b[j]) {  
158.                 return false;  
159.             }  
160.         }  
161.         return true;  
162.     }  
163. }  

package asynchronizedchannel;  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.ServerSocketChannel; import java.nio.channels.SocketChannel; import java.security.MessageDigest; import java.util.Iterator;  public class Server {      /**      * 服务端通信范例程序主函数      *       * @param args      * @throws IOException      */     public static void main(String[] args) throws IOException     {         // Create the selector         final Selector selector = Selector.open();         final ServerSocketChannel server = ServerSocketChannel.open();         server.configureBlocking(false);         server.socket().bind(new InetSocketAddress("xx.xx.xx.xx", 5656), 5);         // Register both channels with selector         server.register(selector, SelectionKey.OP_ACCEPT);         new Thread(new Daemon(selector)).start();     } }  class Daemon implements Runnable {     private final Selector selector;      Daemon(Selector selector)     {         this.selector = selector;     }      public void run()     {         while (true) {             try {                 // Wait for an event                 selector.select();                  // Get list of selection keys with pending events                 Iterator<SelectionKey> it = selector.selectedKeys().iterator();                  // Process each key                 while (it.hasNext()) {                     // Get the selection key                     SelectionKey selKey = it.next();                      // Remove it from the list to indicate that it is being processed                     it.remove();                      // Check if it's a connection request                     if (selKey.isAcceptable()) {                         // Get channel with connection request                         ServerSocketChannel server = (ServerSocketChannel) selKey.channel();                         // Accept the connection request.                         // If serverSocketChannel is blocking, this method blocks.                         // The returned channel is in blocking mode.                         SocketChannel channel = server.accept();                          // If serverSocketChannel is non-blocking, sChannel may be null                         if (channel != null) {                             // Use the socket channel to communicate with the client                             new Thread(new ServerHandler(channel)).start();                         } else {                             System.out.println("---No Connection---");                             // There were no pending connection requests; try again later.                             // To be notified of connection requests,                         }                     }                 }             } catch (Exception ex) {                 ex.printStackTrace();             }         }     } }  class ServerHandler implements Runnable {     private static final long timeout = 30 * 1000; // 设置超时时间为30秒     private static int counter = 0;     private final TcpChannel channel;     private final MessageDigest md;      ServerHandler(SocketChannel channel) throws Exception     {         this.channel = new TcpChannel(channel, System.currentTimeMillis() + timeout, SelectionKey.OP_READ);         md = MessageDigest.getInstance("md5");     }      public void run()     {         try {             while (true) {                 work();                 synchronized (ServerHandler.class) {                     if ((++counter & 65535) == 0) {                         System.out.println(counter);                     }                 }             }         } catch (Exception e) {             e.printStackTrace();         } finally {             channel.cleanup();         }     }      private void work() throws IOException     { // 模拟工作流程         byte[] cache = new byte[256], reply = new byte[5];         read(cache, reply);     }      private void read(byte[] cache, byte[] reply) throws IOException     { // 从套接字读入数据         channel.recv(ByteBuffer.wrap(cache));         md.reset();         md.update(cache, 0, 240);         byte[] md5 = md.digest(); // 使用前240字节产生MD5校验码         if (!ExtArrays.partialEquals(md5, 0, cache, 240, 16)) { // 与后16字节比较             reply[0] = '?';             System.out.println("MISMATCH!");         } else {             reply[0] = '.';         }         channel.send(ByteBuffer.wrap(reply)); // 返回接收结果     } }  final class ExtArrays {     private ExtArrays()     {     }      public static boolean partialEquals(byte[] a, int offset_a, byte[] b, int offset_b, int len)     { // 字节数组的部分比较         if (a == null || b == null) {             return false;         }         if (offset_a + len > a.length || offset_b + len > b.length) {             return false;         }         for (int i = offset_a, j = offset_b, k = len; k > 0; i++, j++, k--) {             if (a[i] != b[j]) {                 return false;             }         }         return true;     } } 

Client端，代码演示：

Java代码

1. package asynchronizedchannel;  
2.   
3. import java.io.IOException;  
4. import java.net.InetSocketAddress;  
5. import java.nio.ByteBuffer;  
6. import java.nio.channels.SelectionKey;  
7. import java.nio.channels.SocketChannel;  
8. import java.security.DigestException;  
9. import java.security.MessageDigest;  
10. import java.util.Random;  
11.   
12. public class Client  
13. {  
14.     private static int id = 0;  
15.     /** 
16.      * 客户端通信范例程序主函数 
17.      *  
18.      * @param args 
19.      * @throws Exception 
20.      */  
21.     public static void main(String[] args) throws Exception  
22.     {  
23.         new Thread(new ClientHandler(id++)).start();  
24.         new Thread(new ClientHandler(id++)).start();  
25.         new Thread(new ClientHandler(id++)).start();  
26.         new Thread(new ClientHandler(id++)).start();  
27.         new Thread(new ClientHandler(id++)).start();  
28.     }  
29.   
30. }  
31.   
32. class ClientHandler implements Runnable  
33. {  
34.     private static final long timeout = 30 * 1000; // 设置超时时间为30秒  
35.     private final TcpChannel channel;  
36.       
37.     private final int id;  
38.   
39.     private final MessageDigest md;  
40.     private final Random rand;  
41.   
42.     ClientHandler(int id) throws Exception  
43.     {  
44.         this.id = id;  
45.         channel = new TcpChannel(SocketChannel.open(), System.currentTimeMillis() + timeout, SelectionKey.OP_WRITE);  
46.         md = MessageDigest.getInstance("md5");  
47.         rand = new Random();  
48.     }  
49.   
50.     @Override  
51.     public void run()  
52.     {  
53.         try {  
54.             channel.connect(new InetSocketAddress("xx.xx.xx.xx", 5656));  
55.             int i = 0;  
56.             while (true) {  
57.                 work();  
58.                 if ((++i & 16383) == 0) {  
59.                     System.out.println(String.format("client(%1$d): %2$d", id, i));  
60.                 }  
61.                 Thread.yield();  
62.             }  
63.         } catch (Exception e) {  
64.             e.printStackTrace();  
65.         } finally {  
66.             channel.cleanup();  
67.         }  
68.     }  
69.   
70.     private void work() throws IOException, DigestException  
71.     {  
72.         byte[] cache = new byte[256], reply = new byte[5];  
73.         write(cache, reply);  
74.     }  
75.   
76.     private void write(byte[] cache, byte[] reply) throws DigestException, IOException  
77.     {  
78.         rand.nextBytes(cache); // 只用前面的240字节  
79.         md.reset();  
80.         md.update(cache, 0, 240);  
81.         md.digest(cache, 240, 16); // MD5校验码占后面16字节  
82.         ByteBuffer buffer = ByteBuffer.wrap(cache);  
83.         channel.send(buffer);  
84.         buffer = ByteBuffer.wrap(reply);  
85.         channel.recv(buffer);  
86.         if (reply[0] != '.') { // 若接收的结果不正确，可以考虑尝试再次发送  
87.             System.out.println("MISMATCH!");  
88.         }  
89.     }  
90. }  

package asynchronizedchannel;  import java.io.IOException; import java.net.InetSocketAddress; import java.nio.ByteBuffer; import java.nio.channels.SelectionKey; import java.nio.channels.SocketChannel; import java.security.DigestException; import java.security.MessageDigest; import java.util.Random;  public class Client {     private static int id = 0;     /**      * 客户端通信范例程序主函数      *       * @param args      * @throws Exception      */     public static void main(String[] args) throws Exception     {         new Thread(new ClientHandler(id++)).start();         new Thread(new ClientHandler(id++)).start();         new Thread(new ClientHandler(id++)).start();         new Thread(new ClientHandler(id++)).start();         new Thread(new ClientHandler(id++)).start();     }  }  class ClientHandler implements Runnable {     private static final long timeout = 30 * 1000; // 设置超时时间为30秒     private final TcpChannel channel;          private final int id;      private final MessageDigest md;     private final Random rand;      ClientHandler(int id) throws Exception     {         this.id = id;         channel = new TcpChannel(SocketChannel.open(), System.currentTimeMillis() + timeout, SelectionKey.OP_WRITE);         md = MessageDigest.getInstance("md5");         rand = new Random();     }      @Override     public void run()     {         try {             channel.connect(new InetSocketAddress("xx.xx.xx.xx", 5656));             int i = 0;             while (true) {                 work();                 if ((++i & 16383) == 0) {                     System.out.println(String.format("client(%1$d): %2$d", id, i));                 }                 Thread.yield();             }         } catch (Exception e) {             e.printStackTrace();         } finally {             channel.cleanup();         }     }      private void work() throws IOException, DigestException     {         byte[] cache = new byte[256], reply = new byte[5];         write(cache, reply);     }      private void write(byte[] cache, byte[] reply) throws DigestException, IOException     {         rand.nextBytes(cache); // 只用前面的240字节         md.reset();         md.update(cache, 0, 240);         md.digest(cache, 240, 16); // MD5校验码占后面16字节         ByteBuffer buffer = ByteBuffer.wrap(cache);         channel.send(buffer);         buffer = ByteBuffer.wrap(reply);         channel.recv(buffer);         if (reply[0] != '.') { // 若接收的结果不正确，可以考虑尝试再次发送             System.out.println("MISMATCH!");         }     } } 

重点说明：

发多少，收多少。要么固定发送和接收的字节数，要么在发送的时候带有发送字节数的信息，接收的时候根据该信息接收完整然后再处理。

 转http://regular.javaeye.com/blog/653936