Java Socket网络编程
1. Ip地址，域名和端口号JDK的java.net包中定义了与IP地址/域名有关的类
1.java.net.InetAddress
32位或128位无符号数字表示的IP地址。
2.java.net.Inet4Address
继承了InetAddress类，以32位无符号数字表示的IPv4地址。
3.java.net.Inet6Address
集成了InetAddress类，以128为无符号数字表示的IPv6地址。
public class TestInetAddress {public static voidmain(String args[]){try {InetAddress ia = InetAddress.getLocalHost();showInfo(ia);ia = InetAddress.getByName("www.sina.com");showInfo(ia);} catch (UnknownHostException e) {e.printStackTrace();}}public static void showInfo(InetAddress ia){String name = ia.getHostName();String address = ia.getHostAddress();print("name:" + name);print("address:" + address);} public staticvoid print(Object o){ System.out.println(o); }} 运行结果：
name:QQ-PCaddress:60.166.219.14name:www.sina.comaddress:61.172.201.1952. URL
URL(Uniform Resource Locator,统一资源定位器）用于表示Internet上资源的地址。
URL格式：<协议名><资源所在主机名>[:<端口号>]<资源名>
http://home.netscape.com/home/welcome.html
java.net包定义了对应的URL类，常用方法如下：
public URL(String spec)
public final InputStream openStream() throws IOException
public class URLReader {public static void main(String args[]){URL url;try {url = new URL("http://www.baidu.com");BufferedReader reader = new BufferedReader(new InputStreamReader(url.openStream()));String s = reader.readLine();while(null != s){System.out.println(s);s = reader.readLine();}} catch (Exception e) {e.printStackTrace();}}} 运行结果：
<!doctype html><html><head><meta http-equiv="Content-Type" content="text/html;charset=gb2312"><title>百度一下，你就知道 3 Socket编程
两个进程间可以通过一个双向的网络通信连接实现数据交换，这种通信链路的端点被称为“套接字”（Socket）。
Socket通常用来实现Client-Server连接。
建立连接时所需的寻址信息
1.远程计算机的机器名或IP地址
2.试图连接的端口号（Port number)
java.net包中定义的两个类Socket和ServerSocket，分别用来实现双向连接的client和server端。在Socket和ServerSocket类常用的构造方法如下：
Socket(InetAddress address,int port) throws IOException;
Socket(String host,int port) throws IOException
ServerSocket(int port) throws IOException
ServerSocket(int port,int backlog) throws IOException
Socket网络编程可分为四个基本步骤：
1. 建立网络连接。
2. 打开连接到Socket
3. 通过打开的I/O流进行数据读/写操作
4. 关闭已打开的I/O流和Socket
Server:
public class TestServer {public static void main(String args[]){ServerSocket server;try {server = new ServerSocket(8888);System.out.println("Server is running!");while(true){Socket s1 = server.accept();//如果没有客户端进来，将会处于阻塞状态OutputStream os =s1.getOutputStream();DataOutputStream dos = new DataOutputStream(os);dos.writeUTF("Hi,Client Address is:" + s1.getInetAddress() + "\tClient port:" + s1.getPort());dos.writeUTF("byte！");dos.close();s1.close();}} catch (IOException e) {e.printStackTrace();}}} Client:
public class TestClient {public static void main(String args[]) {Socket client;try {client = new Socket("127.0.0.1", 8888);InputStream is = client.getInputStream();DataInputStream dis = new DataInputStream(is);print(dis.readUTF());print(dis.readUTF());dis.close();client.close();} catch (UnknownHostException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}}public static void print(Object o) {System.out.println(o);}} 应该先运行Server，然后在运行Client。
简单的聊天程序：
Server：
public class TestServerChat {public static void main(String args[]){try {ServerSocket server = new ServerSocket(8888);Socket s1 = server.accept();OutputStream os = s1.getOutputStream();DataOutputStream dos = new DataOutputStream(os);InputStream is = s1.getInputStream();DataInputStream dis = new DataInputStream(is);BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));String info;while(true){info = dis.readUTF();print("Client：" + info);if(info.equals("byte")){break;}info = reader.readLine();dos.writeUTF(info);if(info.equals("byte")){break;}}dis.close();reader.close();server.close();os.close();} catch (IOException e) {e.printStackTrace();}}public static void print(Object o){System.out.println(o);}} Client：
public class TestClientChat {public static void main(String args[]) {Socket client;try {client = new Socket("127.0.0.1", 8888);InputStream is = client.getInputStream();DataInputStream dis = new DataInputStream(is);OutputStream os = client.getOutputStream();DataOutputStream dos = new DataOutputStream(os);BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));String info;while (true) {info = reader.readLine();dos.writeUTF(info);if (info.equals("byte")) {break;}info = dis.readUTF();print("Server：" + info);if (info.equals("byte")) {break;}}} catch (UnknownHostException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}}public static void print(Object o) {System.out.println(o);}} 此简易聊天程序有很大的局限性，仅可以一人一句。
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