1. 网络概念
把多台计算机通过物理线路连接起来，就形成了网络。目的在于交换数据和共享信息。
1）网络通信的三要素
【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
常见端口:http:80 stmp: 25 ftp:21
有效端口0-65536,开发者可以的端口是1025-65536之间。一些第三方引用如mysql:3306 oracle:1251。
【3】通信协议:通信的规则TCP,UDP
2） 网络通信模型
|
IP地址分类
|
特殊IP
0.0.0.0：本机
127.0.0.1：本机回环地址，用于本机测试
255.255.255.255：当前子网，一般用于向当前子网广播信息
2. InetAddress
InetAddress 表示IP地址。
1 publicclass Test01 { 2 3 publicstaticvoid main(String[] args) { 4 5 // 获取本机IP地址 6 7 InetAddress ip1; 8 9 try {10 11 ip1 = InetAddress.getLocalHost();12 13 // USER-20180113BT/192.168.2.5614 15 System.out.println(ip1.toString());16 17 18 19 // 获取主机名称20 21 System.out.println(ip1.getHostName());22 23 System.out.println(ip1.getHostAddress());24 25 26 27 } catch (UnknownHostException e) {28 29 e.printStackTrace();30 31 }32 33 }34 35 } 3. TCP编程
TCP编程中，如果要完成通信，通信双方必须要创建socket，通过socket完成通信。
TCP通信步骤
[1]服务器启动ServerSocket作为通信的Server端，等待客户端链入。
[2]客户端创建Socket作为通信的Client端
[3]Client端链入Server端后建立可靠的、双向的、持续性的、点对点的通讯连接，即可通信。
案例:完成一次单向通信。
服务器端
1 package cn.sxt01.net01; 2 3 4 5 import java.io.IOException; 6 7 import java.io.OutputStream; 8 9 import java.net.ServerSocket;10 11 import java.net.Socket;12 13 14 15 publicclass Server01 {16 17 publicstaticvoid main(String[] args) {18 19 20 21 System.out.println("服务器启动...");22 23 24 25 // 【1】创建server socket26 27 ServerSocket serverSocket = null;28 29 Socket clientSocket = null;30 31 try {32 33 34 35 serverSocket = new ServerSocket(8000);36 37 // 【2】等待客户端的链入->阻塞式函数->监听8000端口，看是否有client链入38 39 clientSocket = serverSocket.accept();40 41 42 43 System.out.println(clientSocket.getInetAddress().getHostAddress()+"链入!");44 45 46 47 // 【3】给客户端主动发信息48 49 OutputStream out = clientSocket.getOutputStream();50 51 52 53 String msg = "hello 兄弟";54 55 byte[] buf = msg.getBytes("UTF-8");56 57 out.write(buf);58 59 clientSocket.shutdownOutput();60 61 62 63 out.close();64 65 66 67 68 69 } catch (IOException e) {70 71 e.printStackTrace();72 73 }74 75 }76 77 } 客户端
1 package cn.sxt02.net01; 2 3 4 5 import java.io.IOException; 6 7 import java.io.InputStream; 8 9 import java.net.Socket;10 11 12 13 publicclass Client01 {14 15 publicstaticvoid main(String[] args) {16 17 System.out.println("客户端运行...");18 19 20 21 // 【1】创建客户端socket22 23 Socket socket = null;24 25 try {26 27 socket = new Socket("192.168.2.56", 8000);28 29 30 31 // 【2】接收来自服务器的消息32 33 InputStream in = socket.getInputStream();34 35 byte[] buf = newbyte[1024];36 37 intlen = in.read(buf);38 39 40 41 String msg = new String(buf, 0, len, "UTF-8");42 43 System.out.println(msg);44 45 46 47 } catch (IOException e) {48 49 e.printStackTrace();50 51 }52 53 }54 55 } 常见问题
[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.sxt01.net02.Server01.main(Server01.java:19) |
[2]服务器未启动
| java.net.ConnectException: Connection refused: connect at java.net.DualStackPlainSocketImpl.connect0(Native Method) at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:79) at cn.sxt02.net02.Client01.main(Client01.java:15) |
[3]连接超时异常SocketTimeoutException
当网速很慢时，可能发生连接超时异常。
需求:在控制台输入用户名和密码，如果输入正确提示登录成功，否则登录失败。
服务器端
1 public class Test01 { 2 public static void main(String[]args) throws IOException, ClassNotFoundException{ 3 4 System.out.println("服务器启动中..."); 5 ServerSocket serverSocket=new ServerSocket(11000); 6 while(true){ 7 Socket clinetSocket=serverSocket.accept(); 8 MyThread myThread=new MyThread(clinetSocket); 9 myThread.start();10 }11 }12 } 1 public class MyThread extends Thread { 2 3 private Socket socket; 4 5 public MyThread() { 6 super(); 7 } 8 9 public MyThread(Socket socket) {10 super();11 this.socket = socket;12 }13 @Override14 public void run() {15 InputStream in=null;16 ObjectInputStream ois=null;17 OutputStream out=null;18 DataOutputStream dos=null;19 20 try {21 //接收来自客户端的信息22 in=socket.getInputStream();23 ois=new ObjectInputStream(in);24 User user= (User) ois.readObject();25 socket.shutdownInput();26 27 String str;28 if(user.getName().equals("111") && user.getPwd().equals("123")){29 str="成功登陆";30 }else{31 str="用户名或密码错误，登陆失败";32 }33 //返回给客户端的信息34 out=socket.getOutputStream();35 dos=new DataOutputStream(out);36 dos.writeUTF(str);37 socket.shutdownOutput();38 39 in.close();40 ois.close();41 dos.close();42 out.close();43 socket.close();44 } catch (ClassNotFoundException e) {45 e.printStackTrace();46 } catch (IOException e) {47 e.printStackTrace();48 }49 }50 } 1 public class User implements Serializable { 2 3 private static final long serialVersionUID = 4478328638580552366L; 4 private String name; 5 private String pwd; 6 7 public String getName() { 8 return name; 9 }10 11 public void setName(String name) {12 this.name = name;13 }14 15 public String getPwd() {16 return pwd;17 }18 19 public void setPwd(String pwd) {20 this.pwd = pwd;21 }22 23 public User() {24 super();25 }26 27 public User(String name, String pwd) {28 super();29 this.name = name;30 this.pwd = pwd;31 }32 33 @Override34 public String toString() {35 return "User [name=" + name + ", pwd=" + pwd + "]";36 }37 38 } 客户端
1 public class Test01 { 2 public static void main(String [] args){ 3 4 Scanner sc=new Scanner(System.in); 5 System.out.println("请输入登录名："); 6 String name=sc.nextLine(); 7 8 System.out.println("请输入密码："); 9 String pwd=sc.nextLine();10 11 User user=new User(name,pwd);12 13 try {14 // 传输请求给服务器15 Socket socket=new Socket("127.0.0.1",11000);16 OutputStream out=socket.getOutputStream();17 ObjectOutputStream oos=new ObjectOutputStream(out);18 19 oos.writeObject(user);20 socket.shutdownOutput();21 22 //接收来自服务器的信息23 InputStream in=socket.getInputStream();24 DataInputStream dis=new DataInputStream(in);25 26 String str=dis.readUTF();27 System.out.println(str);28 29 30 } catch (UnknownHostException e) {31 e.printStackTrace();32 } catch (IOException e) {33 e.printStackTrace();34 }35 36 37 }38 } 1 public class User implements Serializable { 2 3 private static final long serialVersionUID = 4478328638580552366L; 4 private String name; 5 private String pwd; 6 7 public String getName() { 8 return name; 9 }10 11 public void setName(String name) {12 this.name = name;13 }14 15 public String getPwd() {16 return pwd;17 }18 19 public void setPwd(String pwd) {20 this.pwd = pwd;21 }22 23 public User() {24 super();25 }26 27 public User(String name, String pwd) {28 super();29 this.name = name;30 this.pwd = pwd;31 }32 33 @Override34 public String toString() {35 return "User [name=" + name + ", pwd=" + pwd + "]";36 }37 38 } 4. UDP编程
UDP编程中，如果要完成通信，通信双方必须要创建DatagramSocket，通过DatagramSocket完成通信。
数据报包用来实现无连接包投递服务。每条报文仅根据该包中包含的信息从一台机器路由到另一台机器
UDP步骤:
[1]创建一个DatagramSocket用于表示发送端，通过send方法发送数据报
[2]创建一个DatagramSocket用于表示接收端，通过receive方法接收数据报
先运行接收端，再运行发送端！！！
需求:完成一次单向的UDP通信。
发送端
1 public static void main(String[] args) { 2 3 4 5 // 发送端:主动发送信息 6 7 System.out.println("发送端开始发送信息..."); 8 9 // 【1】创建socket并指定发送数据的端口10 11 DatagramSocketsocket = null;12 13 try {14 15 socket = newDatagramSocket(8000);16 17 18 19 // 【2】创建数据报包20 21 String msg = "hello B";22 23 byte[] buf = msg.getBytes("UTF-8");24 25 DatagramPacketdp = newDatagramPacket(buf, buf.length, InetAddress.getLocalHost(), 9000);26 27 28 29 // 【3】发送30 31 socket.send(dp);32 33 34 35 // 【4】关闭36 37 socket.close();38 39 } catch (SocketExceptione) {40 41 e.printStackTrace();42 43 } catch (UnsupportedEncodingExceptione) {44 45 e.printStackTrace();46 47 } catch (UnknownHostExceptione) {48 49 e.printStackTrace();50 51 } catch (IOExceptione) {52 53 e.printStackTrace();54 55 }56 57 } 接收端
1 public static void main(String[] args) { 2 3 // 接收端:接收信息 4 5 System.out.println("启动接收端..."); 6 7 // 【1】创建一个DatagramSocket 8 9 DatagramSocketsocket = null;10 11 try {12 13 socket = newDatagramSocket(9000);14 15 // 【2】接收消息16 17 byte[] buf = newbyte[1024];18 19 DatagramPacketdp = newDatagramPacket(buf, buf.length);20 21 System.out.println("等待接收信息...");22 23 socket.receive(dp);24 25 System.out.println("接收完成...");26 27 28 29 // 处理接收的信息30 31 String msg = new String(buf, 0, dp.getLength(), "UTF-8");32 33 System.out.println(msg);34 35 36 37 } catch (SocketExceptione) {38 39 e.printStackTrace();40 41 } catch (IOExceptione) {42 43 e.printStackTrace();44 45 }46 47 } 需求：实现双向通信
发送端
1 public static void main(String[] args) { 2 3 4 5 // 发送端:主动发送信息 6 7 System.out.println("发送端开始发送信息..."); 8 9 Scanner sc = new Scanner(System.in);10 11 // 【1】创建socket并指定发送数据的端口12 13 DatagramSocketsocket = null;14 15 try {16 17 socket = newDatagramSocket(8000);18 19 20 21 for(;;) {22 23 System.out.print("A说:");24 25 String msg = sc.nextLine();26 27 byte[] buf = msg.getBytes("UTF-8");28 29 DatagramPacketdp = newDatagramPacket(buf, buf.length, InetAddress.getLocalHost(), 9000);30 31 32 33 // 【3】发送34 35 socket.send(dp);36 37 38 39 40 41 // 接收消息42 43 byte[] revBuf = newbyte[1024];44 45 DatagramPacketrevDp = newDatagramPacket(revBuf,revBuf.length);46 47 socket.receive(revDp);48 49 String revStr = newString(revBuf, 0, revDp.getLength(), "UTF-8");50 51 System.out.println(dp.getAddress().getHostName()+":"+revStr);52 53 }54 55 56 57 } catch (SocketExceptione) {58 59 e.printStackTrace();60 61 } catch (UnsupportedEncodingExceptione) {62 63 e.printStackTrace();64 65 } catch (UnknownHostExceptione) {66 67 e.printStackTrace();68 69 } catch (IOExceptione) {70 71 e.printStackTrace();72 73 }finally {74 75 // 【4】关闭76 77 socket.close();78 79 }80 81 } 接收端
1 public static void main(String[] args) { 2 3 // 接收端:接收信息 4 5 System.out.println("启动接收端..."); 6 7 Scannersc = new Scanner(System.in); 8 9 // 【1】创建一个DatagramSocket10 11 DatagramSocketsocket = null;12 13 14 15 try {16 17 socket = newDatagramSocket(9000);18 19 20 21 for(;;) {22 23 // 接收信息24 25 byte[] buf = newbyte[1024];26 27 DatagramPacketdp = newDatagramPacket(buf, buf.length);28 29 socket.receive(dp);30 31 String msg = new String(buf, 0, dp.getLength(), "UTF-8");32 33 System.out.println(dp.getAddress().getHostName()+":"+msg);34 35 36 37 // 发送信息38 39 System.out.println("B说:");40 41 String sendMsg = sc.nextLine();42 43 byte[] sendBuf = sendMsg.getBytes("UTF-8");44 45 DatagramPacketsendDp = newDatagramPacket(sendBuf, 0, sendBuf.length, dp.getAddress(), dp.getPort());46 47 socket.send(sendDp);48 49 }50 51 52 53 } catch (SocketExceptione) {54 55 e.printStackTrace();56 57 } catch (IOExceptione) {58 59 e.printStackTrace();60 61 }finally {62 63 socket.close();64 65 }66 67 }