网络编程概念。一个UDP构造的聊天室

网络编程：利用网络将不同计算机数据进行交换

网络三要素：

IP地址   +   端口 =Socket

协议 ：UDP，TCP     

inetAddress类的使用

public class InetAddressDemo {public static void main(String[] args) throws Exception {// TODO Auto-generated method stubInetAddress address = InetAddress.getByName("");System.out.println(address.getHostAddress());System.out.println(address.getHostName());InetAddress localHost = InetAddress.getLocalHost();System.out.println(localHost);}}

用本机名和本机地址

UDP和TCP协议

UDP：将数据源和目的封装在数据包中，不需要建立连接，每个数据包大小在64K内，无连接，是不可靠协议，但是速度很快。

TCP:建立连接，形成传输数据的通道，在连接中进行大数据量的传输；通过三次握手完成连接，是可靠协议，但是效率会稍低。

Socket：应用层和传输层之间的桥梁。下面的底层已经封装好了，我们只需要用Socket进行操作就行了。

Socket原理机制：

通信的两端都有Socket

网络通信其实就是Socket间的通信

数据在两个Socket之间通过IO传输

UDP传输服务器端编写

public class Server {public static void main(String[] args) throws Exception {//创建一个服务端Socket并监听指定端口DatagramSocket ds = new DatagramSocket(8888);//接收数据，并将数据放在数据包中byte[] buf =new byte[64*1024];int length = buf.length;DatagramPacket p = new DatagramPacket(buf, length);ds.receive(p);//将包中的数据取出来byte[] data=p.getData();//获取的是接受到的数据InetAddress address = p.getAddress();//接受发送过来的主机地址int port = p.getPort();//获取端口号String ip = address.getHostAddress();//获取的是客户端的ip地址int dataLength = p.getLength();//将数据转换成字符串String result = new String(data,0,dataLength);System.out.println("ip="+ip+",port="+port+",result="+result);//关闭资源ds.close();}}

UDP客户端客户端编写

public class Client {public static void main(String[] args) throws Exception {DatagramSocket ds = new DatagramSocket();byte[] buf = "UDP发送消息".getBytes();//包数据int length=buf.length;//包长度InetAddress address=InetAddress.getByName("127.0.0.1");//目的地址int port=8888;//目的端口号DatagramPacket p=new DatagramPacket(buf, length, address, port);// 调用Socket的发送方法ds.send(p);ds.close();}}

l聊天室初级版客户端

public class Client {public static void main(String[] args) throws Exception {DatagramSocket ds = new DatagramSocket();InetAddress address = InetAddress.getByName("127.0.0.1");Scanner sc = new Scanner(System.in);String line;while (!(line = sc.nextLine()).equals("886")) {byte[] buf = line.getBytes();DatagramPacket packet = new DatagramPacket(buf, buf.length, address, 8888);ds.send(packet);}ds.close();}}

服务器端

public class Server {public static void main(String[] args) throws Exception {DatagramSocket socket = new DatagramSocket(8888);//循环接受客户端发送的内容byte[] buf=new byte[64*1024];while(true){DatagramPacket packet = new DatagramPacket(buf, buf.length);//接受客户端数据并存储到包中socket.receive(packet);//从数据包中取出内容byte[] data = packet.getData();int length = packet.getLength();String ip = packet.getAddress().getHostAddress();//将字节数组的形式内容转化成字符串String result = new String(data,0,length);System.out.println("ip="+ip+",result="+result);}}}

注意点：服务器端创建Socket直接带端口号

如何和在一个界面上？

运用线程。让这俩个程序运行在同一个主线程内。

此时会报错。Command+option+z，try...catch一下。第一个意思是分别catch，第二个是 catch所有的Exception。

一个完整的UDP聊天室

客户端

public class ClientRunnable implements Runnable {private String ip;private int port;public ClientRunnable(String ip, int port) {this.ip = ip;this.port = port;}@Overridepublic void run() {DatagramSocket ds = null;try {ds = new DatagramSocket();InetAddress address = InetAddress.getByName(ip);Scanner sc = new Scanner(System.in);String line;while (!(line = sc.nextLine()).equals("886")) {byte[] buf = line.getBytes();DatagramPacket packet = new DatagramPacket(buf, buf.length, address, port);ds.send(packet);}} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();} finally {if (ds != null) {ds.close();}}}}

服务器端

public class ServerRunnable implements Runnable {private int port;public ServerRunnable(int port) {this.port = port;}@Overridepublic void run() {try {DatagramSocket socket = new DatagramSocket(port);//循环接受客户端发送的内容byte[] buf=new byte[64*1024];while(true){DatagramPacket packet = new DatagramPacket(buf, buf.length);//接受客户端数据并存储到包中socket.receive(packet);//从数据包中取出内容byte[] data = packet.getData();int length = packet.getLength();String ip = packet.getAddress().getHostAddress();//将字节数组的形式内容转化成字符串String result = new String(data,0,length);System.out.println("ip="+ip+",result="+result);}} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}}}

主程序

public class ChatRoom {public static void main(String[] args) {//先启动服务端聊天线程，再启动客户端聊天线程ClientRunnable clientRunnable = new ClientRunnable("127.0.0.1",8888);ThreadPoolUtils.execute(clientRunnable);ServerRunnable serverRunnable = new ServerRunnable(8888);ThreadPoolUtils.execute(serverRunnable);}}

线程池

public class ThreadPoolUtils {private static ExecutorService threadpool = Executors.newCachedThreadPool();public static void execute(Runnable command) {threadpool.execute(command);}}