17_网络编程

 
 网络编程 

 
 网络 

 
 把多台终端(计算机)通过物理线路连接起来，形成网络。便于交换数据、共享信息、组成更强大的逻辑体。 

 
 网络通信三要素 

 
 【1】IP地址:唯一标识网络上的每一台计算机 

 
  两台计算机之间通信的必备有素 

 
 【2】端口号:计算机中应用的标号(代表一个应用程序) 

 
  0-1024系统使用或保留端口 ， 

 
  有效端口0-65536 

 
 常见的端口http协议80端口、mysql(3306) oracle(1521) 

 
 【3】通信协议:通信的规则 

 
  TCP,UDP 

 
 TCP/IP参考模型 

 
 IP地址分类 

 
 127.0.0.1 表示本机IP地址 

 
 InetAddress 

 
 表示IP地址信息 

 
      package cn.net01; 
     
      import java.net.InetAddress; 
     
      import java.net.UnknownHostException; 
     
      import java.util.Arrays; 
     
      public class Test02 { 
     
       public static void main(String[] args) throws UnknownHostException { 
     
       // 通过IP地址构建InetAddress对象 
     
       byte[] ip = new byte[] {(byte) 192,(byte) 168,7,(byte)189}; 
     
       InetAddress ip1 = InetAddress.getByAddress(ip); 
     
       System.out.println(ip1.toString()); 
     
       System.out.println(ip1.getHostName()); 
     
       System.out.println(ip1.getHostAddress()); 
     
       // 给定名称www.baidu.com 获取地址 
     
       InetAddress ip3 = InetAddress.getByName("www.baidu.com"); 
     
       System.out.println(ip3.toString()); 
     
       InetAddress[] ips = InetAddress.getAllByName("www.baidu.com"); 
     
       System.out.println(Arrays.toString(ips)); 
     
       } 
     
      }

 
 TCP编程(A) 

 
 案例:服务器向客户端完成一次单向通信 

 
      package cn.net02; 
     
      import java.io.IOException; 
     
      import java.io.OutputStream; 
     
      import java.net.ServerSocket; 
     
      import java.net.Socket; 
     
      public class Server01 { 
     
       public static void main(String[] args){ 
     
       System.out.println("server running...."); 
     
       // 【1】创建serversocket 
     
       ServerSocket serverSocket = null; 
     
       try { 
     
       serverSocket = new ServerSocket(8000); 
     
       } catch (IOException e) { 
     
       e.printStackTrace(); 
     
       } 
     
       // 【2】等待客户端链入 
     
       Socket clientSocket = null; 
     
       try { 
     
       // accept 阻塞式方法 
     
       clientSocket = serverSocket.accept(); 
     
       System.out.println("客户端"+clientSocket.getInetAddress().getHostAddress()+"链入"); 
     
       } catch (IOException e) { 
     
       // TODO Auto-generated catch block 
     
       e.printStackTrace(); 
     
       } 
     
       // 【3】服务器给客户端发信息 
     
       OutputStream out = null; 
     
       try { 
     
       out = clientSocket.getOutputStream(); 
     
       String msg = "hello!"; 
     
       byte[] buf = msg.getBytes(); 
     
       out.write(buf); 
     
       clientSocket.shutdownOutput(); 
     
       out.close(); 
     
       } catch (IOException e) { 
     
       e.printStackTrace(); 
     
       } 
     
       } 
     
      }

 
      package cn.net02; 
     
      import java.io.IOException; 
     
      import java.io.InputStream; 
     
      import java.net.Socket; 
     
      import java.net.UnknownHostException; 
     
      import com.sun.org.apache.bcel.internal.generic.NEW; 
     
      public class Client01 { 
     
       public static void main(String[] args) { 
     
       System.out.println("client running..."); 
     
       // 【1】创建客户端socket 
     
       Socket socket=null; 
     
       try { 
     
       socket = new Socket("192.168.7.194",8000); 
     
       } catch (UnknownHostException e) { 
     
       e.printStackTrace(); 
     
       } catch (IOException e) { 
     
       e.printStackTrace(); 
     
       } 
     
       // 【2】接收服务器发来的信息 
     
       InputStream in = null; 
     
       try { 
     
       in = socket.getInputStream(); 
     
       byte[] buf = new byte[4]; 
     
       int len; 
     
       StringBuilder sb = new StringBuilder(); 
     
       while( (len=in.read(buf)) != -1) { 
     
       sb.append(new String(buf,0,len)); 
     
       } 
     
       System.out.println("来自服务器的消息："+sb.toString()); 
     
       } catch (IOException e) { 
     
       e.printStackTrace(); 
     
       } 
     
       } 
     
      }

 
 常见异常 

 
 [1]端口被占用 

 
      java.net.BindException: Address already in use: JVM_Bind 
     
       at java.net.DualStackPlainSocketImpl.bind0(Native Method) 
     
       at java.net.DualStackPlainSocketImpl.socketBind(DualStackPlainSocketImpl.java:106) 
     
       at java.net.AbstractPlainSocketImpl.bind(AbstractPlainSocketImpl.java:387) 
     
       at java.net.PlainSocketImpl.bind(PlainSocketImpl.java:190) 
     
       at java.net.ServerSocket.bind(ServerSocket.java:375) 
     
       at java.net.ServerSocket.<init>(ServerSocket.java:237) 
     
       at java.net.ServerSocket.<init>(ServerSocket.java:128) 
     
       at cn.net02.Server01.main(Server01.java:15) 
     
      Exception in thread "main" java.lang.NullPointerException 
     
       at cn.net02.Server01.main(Server01.java:24)

 
 [2]服务器没启动 

 
      java.net.ConnectException: Connection refused: connect 
     
       at java.net.DualStackPlainSocketImpl.connect0(Native Method) 
     
       at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:79) 
     
       at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350) 
     
       at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206) 
     
       at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188) 
     
      …

 
 [3] SocketTimeoutException 连接超时异常。 

 
 案例:服务器和客户端双向通信 

 
      package cn.net03; 
     
      import java.io.DataInput; 
     
      import java.io.DataInputStream; 
     
      import java.io.DataOutputStream; 
     
      import java.io.IOException; 
     
      import java.io.InputStream; 
     
      import java.io.OutputStream; 
     
      import java.net.ServerSocket; 
     
      import java.net.Socket; 
     
      public class Server01 { 
     
       public static void main(String[] args) throws IOException { 
     
       System.out.println("server running...."); 
     
       ServerSocket serverSocket = new ServerSocket(8000); 
     
       Socket clientSocket = serverSocket.accept(); 
     
       // send msg to client 
     
       OutputStream out = clientSocket.getOutputStream(); 
     
       String msg = "hello client"; 
     
       DataOutputStream dos = new DataOutputStream(out); 
     
       dos.writeUTF(msg); 
     
       clientSocket.shutdownOutput(); 
     
       // receive msg2 from client 
     
       InputStream in = clientSocket.getInputStream(); 
     
       DataInputStream dis = new DataInputStream(in); 
     
       String msg2 = dis.readUTF(); 
     
       System.out.println("来自客户端消息:"+msg2); 
     
       clientSocket.shutdownInput(); 
     
       dos.close(); 
     
       out.close(); 
     
       in.close(); 
     
       dis.close(); 
     
       } 
     
      }

 
      package cn.net03; 
     
      import java.io.DataInputStream; 
     
      import java.io.DataOutputStream; 
     
      import java.io.IOException; 
     
      import java.io.InputStream; 
     
      import java.io.OutputStream; 
     
      import java.net.Socket; 
     
      import java.net.UnknownHostException; 
     
      import javax.print.Doc; 
     
      public class Client01 { 
     
       public static void main(String[] args) throws UnknownHostException, IOException { 
     
       System.out.println("client running..."); 
     
       Socket socket = new Socket("127.0.0.1",8000); 
     
       // receive msg from server 
     
       InputStream in = socket.getInputStream(); 
     
       DataInputStream dis = new DataInputStream(in); 
     
       String msg = dis.readUTF(); 
     
       System.out.println(msg); 
     
       socket.shutdownInput(); 
     
       // send msg to server 
     
       OutputStream out = socket.getOutputStream(); 
     
       DataOutputStream dos = new DataOutputStream(out); 
     
       String msg2 = "hello server"; 
     
       dos.writeUTF(msg2); 
     
       socket.shutdownOutput(); 
     
       in.close(); 
     
       dis.close(); 
     
       out.close(); 
     
       dos.close(); 
     
       } 
     
      }

 
 需求:请发送一张图片到服务器。 

 
 需求:c/s模式验证用户名密码。 

 
 User序列化是客户端和服务器端的全路径一定要一致。 

 
 UDP编程(B) 

 
 需求:客户端A向客户端B发信息 

 
 客户端A 

 
      package cn.net06; 
     
      import java.io.IOException; 
     
      import java.net.DatagramPacket; 
     
      import java.net.DatagramSocket; 
     
      import java.net.InetAddress; 
     
      import java.util.Scanner; 
     
      public class ClientA { 
     
       public static void main(String[] args) throws IOException { 
     
       // 客户端A 
     
       DatagramSocket ds = new DatagramSocket(8000); 
     
       while(true) { 
     
       //System.out.println("请输入"); 
     
       Scanner sc = new Scanner(System.in); 
     
       String msg = sc.nextLine(); 
     
       // --send msg to ClientB -- 
     
       System.out.println("开始发送数据:"+msg); 
     
       byte[] buf = msg.getBytes(); 
     
       InetAddress toIp = InetAddress.getLocalHost(); 
     
       DatagramPacket dp = new DatagramPacket(buf, buf.length, toIp, 9000); 
     
       // 构造一个数据报包socket，通过8000用于发送数据报 
     
       ds.send(dp); 
     
       // --receive msg from clientA-- 
     
       byte[] recBuf = new byte[1024]; 
     
       DatagramPacket recDp = new DatagramPacket(recBuf, recBuf.length); 
     
       ds.receive(recDp); 
     
       String recMsg = new String(recBuf, 0, recDp.getLength()); 
     
       System.out.println("clientB说:"+recMsg); 
     
       } 
     
       // ds.close(); 
     
       } 
     
      }

 
 客户端B 

 
      package cn.net06; 
     
      import java.io.IOException; 
     
      import java.net.DatagramPacket; 
     
      import java.net.DatagramSocket; 
     
      import java.net.InetAddress; 
     
      import java.net.SocketException; 
     
      import java.util.Scanner; 
     
      public class ClientB { 
     
       public static void main(String[] args) throws IOException { 
     
       // 创建一个datagram socket用于结束clientA 传入的数据 
     
       DatagramSocket ds = new DatagramSocket(9000); 
     
       while (true) { 
     
      // System.out.println("正在接收信息..."); 
     
       // --receive msg from clinetA-- 
     
       byte[] buf = new byte[1024]; 
     
       DatagramPacket dp = new DatagramPacket(buf, buf.length); 
     
       ds.receive(dp); 
     
       // 从dp中获取接收的内容 
     
       String msg = new String(buf, 0, dp.getLength()); 
     
       System.out.println("clientA说:" + msg); 
     
       // --send msg to clientA-- 
     
       Scanner sc = new Scanner(System.in); 
     
       String sendMsg = sc.nextLine(); 
     
       byte[] sendBuf = sendMsg.getBytes(); 
     
       InetAddress toIp = InetAddress.getLocalHost(); 
     
       DatagramPacket sendPd = new DatagramPacket(sendBuf, sendBuf.length, toIp, 8000); 
     
       // DatagramSocket sendDs = new DatagramSocket(9000); 
     
       ds.send(sendPd); 
     
       } 
     
       } 
     
      }

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