Java NIO实例-DatagramChannel实现UDP协议传输

自己的学习笔记（日后发现问题会修正）

在网上找到一些关于udp协议，学习后写了一个实例用于学习之用。

根据别人的经验，总结了以下几点内容：

TCP与UDP效率比较：

    TCP协议适用于对效率要求相对低，但对准确性要求相对高的场景下，或者是有一种连接概念的场景下；而UDP协议适用于对效率要求相对高，对准确性要求相对低的场景。

TCP与UDP应用场景：

    TCP可以用于网络数据库，分布式高精度计算系统的数据传输；UDP可以用于服务系统内部之间的数据传输，因为数据可能比较多，内部系统局域网内的丢包错包率又很低，即便丢包，顶多是操作无效，这种情况下，UDP经常被使用。

网上收集的资料：

TCP字节流与UDP数据报：http://network.51cto.com/art/201310/413326.htm

TCP和UDP的区别（转）：http://www.cnblogs.com/bizhu/archive/2012/05/12/2497493.html

java nio对OP_WRITE的处理解决网速慢的连接：http://blog.sina.com.cn/s/blog_783ede0301013g5n.html

测试工具：

使用clumsy工具，可以模拟网络丢包、网络延迟等恶劣环境

下载地址：http://download.csdn.net/detail/foart/8999423

服务端

package cn;import java.io.IOException;import java.net.ServerSocket;import java.net.Socket;import java.net.SocketAddress;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;/** * @author  * @date 2015-8-7 上午11:36:25 */import java.nio.channels.*;import java.nio.charset.*;import java.net.*;import java.io.*;import java.util.*;import java.nio.*;public class DatagramChannelServerDemo {// UDP协议服务端private int port = 9975;DatagramChannel channel;private Charset charset = Charset.forName("UTF-8");private Selector selector = null;public DatagramChannelServerDemo() throws IOException {try {selector = Selector.open();channel = DatagramChannel.open();} catch (Exception e) {selector = null;channel = null;System.out.println("超时");}System.out.println("服务器启动");}/* 编码过程 */public ByteBuffer encode(String str) {return charset.encode(str);}/* 解码过程 */public String decode(ByteBuffer bb) {return charset.decode(bb).toString();}/* 服务器服务方法 */public void service() throws IOException {if(channel==null || selector==null) return;channel.configureBlocking(false);channel.socket().bind(new InetSocketAddress(port));// channel.write(ByteBuffer.wrap(new String("aaaa").getBytes()));channel.register(selector, SelectionKey.OP_READ);/** 外循环，已经发生了SelectionKey数目 */while (selector.select() > 0) {System.out.println("有新channel加入");/* 得到已经被捕获了的SelectionKey的集合 */Iterator iterator = selector.selectedKeys().iterator();while (iterator.hasNext()) {SelectionKey key = null;try {key = (SelectionKey) iterator.next();iterator.remove();if (key.isReadable()) {reveice(key);}if (key.isWritable()) {// send(key);}} catch (IOException e) {e.printStackTrace();try {if (key != null) {key.cancel();key.channel().close();}} catch (ClosedChannelException cex) {e.printStackTrace();}}}/* 内循环完 */}/* 外循环完 */}/* * 接收 用receive()读IO * 作为服务端一般不需要调用connect()，如果未调用<span style="font-family: Arial, Helvetica, sans-serif;">connect()时调</span><span style="font-family: Arial, Helvetica, sans-serif;">用read()\write()读写，会报java.nio.channels</span> * .NotYetConnectedException 只有调用connect()之后,才能使用read和write. */synchronized public void reveice(SelectionKey key) throws IOException {if (key == null)return;// ***用channel.receive()获取客户端消息***//// ：接收时需要考虑字节长度DatagramChannel sc = (DatagramChannel) key.channel();String content = "";// create buffer with capacity of 48 bytesByteBuffer buf = ByteBuffer.allocate(1024);// java里一个(utf-8)中文3字节,gbk中文占2个字节buf.clear();SocketAddress address = sc.receive(buf); // read into buffer. 返回客户端的地址信息String clientAddress = address.toString().replace("/", "").split(":")[0];String clientPost = address.toString().replace("/", "").split(":")[1];buf.flip(); // make buffer ready for readwhile (buf.hasRemaining()) {buf.get(new byte[buf.limit()]);// read 1 byte at a timecontent += new String(buf.array());}buf.clear(); // make buffer ready for writingSystem.out.println("接收：" + content.trim());// 第一次发；udp采用数据报模式，发送多少次，接收多少次ByteBuffer buf2 = ByteBuffer.allocate(65507);buf2.clear();buf2.put("消息推送内容 abc..UDP是一个非连接的协议，传输数据之前源端和终端不建立连接，当它想传送时就简单地去抓取来自应用程序的数据，并尽可能快地把它扔到网络上。在发送端UDP是一个非连接的协议，传输数据之前源端和终端不建立连接，当它想传送时就简单地去抓取来自应用程序的数据，并尽可能快地把它扔到网络上。在发送端UDP是一个非连接的协议，传输数据之前源端和终端不建立连接，当它想传送时就简单地去抓取来自应用程序的数据，并尽可能快地把它扔到网络上。在发送端@Q".getBytes());buf2.flip();channel.send(buf2, new InetSocketAddress(clientAddress,Integer.parseInt(clientPost))); // 将消息回送给客户端// 第二次发ByteBuffer buf3 = ByteBuffer.allocate(65507);buf3.clear();buf3.put("任务完成".getBytes());buf3.flip();channel.send(buf3, new InetSocketAddress(clientAddress, Integer.parseInt(clientPost))); // 将消息回送给客户端}int y = 0;public void send(SelectionKey key) {if (key == null)return;// ByteBuffer buff = (ByteBuffer) key.attachment();DatagramChannel sc = (DatagramChannel) key.channel();try {sc.write(ByteBuffer.wrap(new String("aaaa").getBytes()));} catch (IOException e1) {e1.printStackTrace();}System.out.println("send2() " + (++y));}/* 发送文件 */public void sendFile(SelectionKey key) {if (key == null)return;ByteBuffer buff = (ByteBuffer) key.attachment();SocketChannel sc = (SocketChannel) key.channel();String data = decode(buff);if (data.indexOf("get") == -1)return;String subStr = data.substring(data.indexOf(" "), data.length());System.out.println("截取之后的字符串是 " + subStr);FileInputStream fileInput = null;try {fileInput = new FileInputStream(subStr);FileChannel fileChannel = fileInput.getChannel();fileChannel.transferTo(0, fileChannel.size(), sc);fileChannel.close();} catch (IOException e) {e.printStackTrace();} finally {try {fileInput.close();} catch (IOException ex) {ex.printStackTrace();}}}public static void main(String[] args) throws IOException {new DatagramChannelServerDemo().service();}}

客户端

package cn;import java.io.IOException;import java.net.ConnectException;import java.net.InetSocketAddress;import java.net.ServerSocket;import java.net.Socket;import java.net.SocketAddress;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;/** * @author  * @date 2015-8-7 上午11:36:25 */import java.nio.channels.*;import java.nio.charset.*;import java.net.*;import java.io.*;import java.util.*;import java.nio.*;public class DatagramChannelClientDemo {// UDP协议客户端private String serverIp = "127.0.0.1";private int port = 9975;// private ServerSocketChannel serverSocketChannel;DatagramChannel channel;private Charset charset = Charset.forName("UTF-8");private Selector selector = null;public DatagramChannelClientDemo() throws IOException {try {selector = Selector.open();channel = DatagramChannel.open();} catch (Exception e) {selector = null;channel = null;System.out.println("超时");}System.out.println("客户器启动");}/* 编码过程 */public ByteBuffer encode(String str) {return charset.encode(str);}/* 解码过程 */public String decode(ByteBuffer bb) {return charset.decode(bb).toString();}/* 服务器服务方法 */public void service() throws IOException {if(channel==null || selector==null) return;channel.configureBlocking(false);channel.connect(new InetSocketAddress(serverIp, port));// 连接服务端channel.write(ByteBuffer.wrap(new String("客户端请求获取消息").getBytes()));channel.register(selector, SelectionKey.OP_READ);/** 外循环，已经发生了SelectionKey数目 */while (selector.select() > 0) {/* 得到已经被捕获了的SelectionKey的集合 */Iterator iterator = selector.selectedKeys().iterator();while (iterator.hasNext()) {SelectionKey key = null;try {key = (SelectionKey) iterator.next();iterator.remove();if (key.isReadable()) {reveice(key);}if (key.isWritable()) {// send(key);}} catch (IOException e) {e.printStackTrace();try {if (key != null) {key.cancel();key.channel().close();}} catch (ClosedChannelException cex) {e.printStackTrace();}}}/* 内循环完 */}/* 外循环完 */}///* // * 接收用read()读IO// *  *///synchronized public void reveice2(SelectionKey key) throws IOException {//if (key == null)//return;//// ***用channel.read()获取消息***////// ：接收时需要考虑字节长度//DatagramChannel sc = (DatagramChannel) key.channel();//String content = "";//// create buffer with capacity of 48 bytes//ByteBuffer buf = ByteBuffer.allocate(3);// java里一个(utf-8)中文3字节,gbk中文占2个字节//int bytesRead = sc.read(buf); //read into buffer.////while (bytesRead >0) {//  buf.flip();  //make buffer ready for read//  while(buf.hasRemaining()){      //  buf.get(new byte[buf.limit()]); // read 1 byte at a time//      content += new String(buf.array());//  }//  buf.clear(); //make buffer ready for writing//  bytesRead = sc.read(buf);//}//System.out.println("接收：" + content);//}/* 接收 */synchronized public void reveice(SelectionKey key) throws IOException {String threadName = Thread.currentThread().getName();if (key == null)return;try {// ***用channel.receive()获取消息***//// ：接收时需要考虑字节长度DatagramChannel sc = (DatagramChannel) key.channel();String content = "";//第一次接；udp采用数据报模式，发送多少次，接收多少次ByteBuffer buf = ByteBuffer.allocate(65507);// java里一个(utf-8)中文3字节,gbk中文占2个字节buf.clear();SocketAddress address = sc.receive(buf); // read into buffer.String clientAddress = address.toString().replace("/", "").split(":")[0];String clientPost = address.toString().replace("/", "").split(":")[1];System.out.println(threadName + "\t" + address.toString());buf.flip(); // make buffer ready for readwhile (buf.hasRemaining()) {buf.get(new byte[buf.limit()]);// read 1 byte at a timebyte[] tmp = buf.array();content += new String(tmp);}buf.clear(); // make buffer ready for writing次System.out.println(threadName + "接收：" + content.trim());//第二次接content = "";ByteBuffer buf2 = ByteBuffer.allocate(65507);// java里一个(utf-8)中文3字节,gbk中文占2个字节buf2.clear();SocketAddress address2 = sc.receive(buf2); // read into buffer.buf2.flip(); // make buffer ready for readwhile (buf2.hasRemaining()) {buf2.get(new byte[buf2.limit()]);// read 1 byte at a timebyte[] tmp = buf2.array();content += new String(tmp);}buf2.clear(); // make buffer ready for writing次System.out.println(threadName + "接收2：" + content.trim());} catch (PortUnreachableException ex) {System.out.println(threadName + "服务端端口未找到!");}send(2);}boolean flag = false;public void send(int i) {if (flag)return;try {// channel.write(ByteBuffer.wrap(new String("客户端请求获取消息(第"+i+"次)").getBytes()));// channel.register(selector, SelectionKey.OP_READ );ByteBuffer buf2 = ByteBuffer.allocate(48);buf2.clear();buf2.put(("客户端请求获取消息(第" + i + "次)").getBytes());buf2.flip();channel.write(buf2);channel.register(selector, SelectionKey.OP_READ );//int bytesSent = channel.send(buf2, new InetSocketAddress(serverIp,port)); // 将消息回送给服务端} catch (IOException e) {e.printStackTrace();}flag = true;}int y = 0;public void send(SelectionKey key) {if (key == null)return;// ByteBuffer buff = (ByteBuffer) key.attachment();DatagramChannel sc = (DatagramChannel) key.channel();try {sc.write(ByteBuffer.wrap(new String("aaaa").getBytes()));} catch (IOException e1) {e1.printStackTrace();}System.out.println("send2() " + (++y));}/* 发送文件 */public void sendFile(SelectionKey key) {if (key == null)return;ByteBuffer buff = (ByteBuffer) key.attachment();SocketChannel sc = (SocketChannel) key.channel();String data = decode(buff);if (data.indexOf("get") == -1)return;String subStr = data.substring(data.indexOf(" "), data.length());System.out.println("截取之后的字符串是 " + subStr);FileInputStream fileInput = null;try {fileInput = new FileInputStream(subStr);FileChannel fileChannel = fileInput.getChannel();fileChannel.transferTo(0, fileChannel.size(), sc);fileChannel.close();} catch (IOException e) {e.printStackTrace();} finally {try {fileInput.close();} catch (IOException ex) {ex.printStackTrace();}}}public static void main(String[] args) throws IOException {new Thread(new Runnable() {public void run() {try {new DatagramChannelClientDemo().service();} catch (IOException e) {e.printStackTrace();}}}).start();//new Thread(new Runnable() {//public void run() {//try {//new DatagramChannelClientDemo().service();//} catch (IOException e) {//e.printStackTrace();//}//}//}).start();}}