[网络协议]快速了解网络通信，实现客户端和服务端聊天

目录

网络的七层模型

TCP/UDP区别

三次握手和四次挥手

三次握手

四次挥手

socket编程

socket实现客户端与服务端对话

实现互相连续聊天

UDP编程

UDP实现客户端，服务端聊天

总结

网络的七层模型

?

应用层

表示层

会话层

传输层

网络层

数据链路层物理层

?传输层协议：TCP UDP

应用层：HTTP协议

TCP/UDP区别

三次握手和四次挥手

TCP 传输控制协议

分客户端和服务端，属于可靠协议，不会丢失数据

TCP连接需要通过三次握手机制在客户端和服务端建立起链接

三次握手

1. 客户端发送信号量SYN=1 和序列号seq=J 给服务端，客户端进入SYN_SENT(信号发送状态)，等待服务器回答

2. 服务器收到客户端信号后，发送信号量SYN=1、ACK=1，应答值ack=J+1，新的序列号seq=K给客户端，服务器进入SYN_RCVD(收到信号)状态

3. 客户端收到服务器的应答消息，发送ACK=1，和应答值ack=K+1给服务器，客户端和服务器都进入ESTABLISHED（连接建立）状态

四次挥手

客户端和服务端断开链接需要四次挥手机制断开连接

1. 客户端发送信号量FIN M给服务器端，进入FIN_WAIT1状态

2. 服务端收到后，返回ack M+1给客户端，进入CLOSE_WAIT状态

3. 服务端在发送FIN N信号给客户端

4. 客户端收到后，返回应答信号ACK=1 ack=N+1给服务端，连接关闭

socket编程

? ? ? ? socket(套接字)，用于TCP/IP协议的网络编程机制

? ? ? ? ServerSocket 服务端 对本机的某个端口进行监听

????????????????创建

????????????????????????ServerSocket(int port) 参数是端口号

????????????????方法

? ? ? ????????????????? close（）关闭

? ? ? ? ????????????????Socket accept() 接受客户端连接，会堵塞线程，直到连接到客户端

? ? ? ? Socket 客户端 代表客户端向服务端请求连接 发送网络通知

? ? ? ? ? ? ? ? 创建

? ? ? ? ? ? ? ? ? ? ? ? Socket(String ip,int port) ip地址 端口号

? ? ? ? ? ? ? ? 方法

????????????????????????

????????????????????????disconnect() 关闭

????????????????????????OutputStream getOutputStream() 获得输出流

????????????????????????InputStream getInputStream() 获得输入流

????????????????????????注意：IO流关闭后，socket会自动关闭

socket实现客户端与服务端对话

? ? ? ? ? 客户端：

????????

package htp;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.ServerSocket;
import java.net.Socket;


public class Client {
    public void send(String ip, int port, String msg) {
        try (Socket socket = new Socket(ip, port)) {
            try (ObjectOutputStream out = new ObjectOutputStream(socket.getOutputStream())) {
                out.writeUTF(msg);
                out.flush();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    public void start() throws IOException {
        System.out.println("客户端启动了");
        try(ServerSocket socket = new ServerSocket(8080)){
            //接受消息
            new Thread(()->{
                while (true){
                    try {
                        Socket accept = null;
                        accept = socket.accept();
                        System.out.println("客户机连接了"+accept.getInetAddress());
                        ObjectInputStream input = new ObjectInputStream(accept.getInputStream());
                        String str = null;
                        System.out.println("接受到"+str);
                        str = input.readUTF();
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            }).start();
        }
    }

    public static void main(String[] args) throws IOException {
        Client client = new Client();
        client.start();
        client.send("192.168.1.124", 8888, "java真厉害");
    }
}

服务端：

package htp;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.ServerSocket;
import java.net.Socket;

public class Server {
    public static final int PART = 8080;
    public void start() throws IOException {
        System.out.println("服务器启动了");
        try(ServerSocket socket = new ServerSocket(PART)){
            //接受消息
            new Thread(()->{
                while (true){
                    try {
                    Socket accept = null;
                    accept = socket.accept();
                    System.out.println("客户机连接了"+accept.getInetAddress());
                    ObjectInputStream input = new ObjectInputStream(accept.getInputStream());
                    String str = null;
                    System.out.println("接受到"+str);
                    str = input.readUTF();
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            }).start();
        }
    }

    public void send(String ip,int port,String msg){
        try(Socket socket = new Socket(ip,port)){
            ObjectOutputStream out = new ObjectOutputStream(socket.getOutputStream());
            out.writeUTF(msg);
            out.flush();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    public static void main(String[] args) {
        try {
            Server server = new Server();
            server.start();
            server.send("192.168.1.124",8888,"我是服务器");

        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

实现互相连续聊天

? ? ? ? 创建输入流线程

package htp;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.net.Socket;

public class ReaderRunnable implements Runnable{
    private Socket socket;

    public ReaderRunnable(Socket socket) {
        this.socket = socket;
    }

    @Override
    public void run() {
        try {
            while (true){
                ObjectInputStream input = new ObjectInputStream(socket.getInputStream());
                String s = input.readUTF();
                System.out.println("接收到了"+socket.getInetAddress()+"消息:"+s);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

创建输出流线程

package htp;

import java.io.IOException;
import java.io.ObjectOutputStream;
import java.net.Socket;
import java.util.Scanner;

public class WriterRunnable implements Runnable{
    private Socket socket;

    public WriterRunnable(Socket socket) {
        this.socket = socket;
    }

    @Override
    public void run() {
        ObjectOutputStream out = null;
        try {
            out = new ObjectOutputStream(socket.getOutputStream());
        } catch (IOException e) {
            e.printStackTrace();
        }
        Scanner scanner = new Scanner(System.in);
        while (true){
            try {
                System.out.println("输入框：");
                String msg = scanner.nextLine();
                out.writeUTF(msg);
                out.flush();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

创建服务端

package htp;

import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class ChatHome {
    public void send(String ip,int port) throws IOException {
        while (true){
            ExecutorService executorService = Executors.newFixedThreadPool(2);
            ServerSocket socket = new ServerSocket(port);
            Socket accept = socket.accept();
            executorService.execute(new ReaderRunnable(accept));
            executorService.execute(new WriterRunnable(accept));
        }
    }
    public static void main(String[] args) {
        try {
            new ChatHome().send("192.168.1.124",8888);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

创建客户端

package htp;

import java.io.IOException;
import java.net.Socket;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class ChatHome2 {
    public void send(String ip,int port) throws IOException {
        Socket socket = new Socket(ip,port);
        ExecutorService executorService = Executors.newFixedThreadPool(2);
        executorService.execute(new ReaderRunnable(socket));
        executorService.execute(new WriterRunnable(socket));
    }
    public static void main(String[] args) {
        try {
            new ChatHome2().send("192.168.1.120",8080);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

先启动服务端，再启动客户端，就可以实现相互聊天了。

UDP编程

数据报协议，类似广播，属于不可靠的协议，无连接

服务端

DatagramSocket(int port) 指定端口获得发送的数据报

客户端

DatagramSocket() 作为客户端使用

主要方法

receive(DatagramPacket) 接收数据包

send(DatagramPacket) 发送数据报

UDP实现客户端，服务端聊天

DatagramPacket 包

DatagramPacket(String ip,int port) 发送前指定ip和端口

public class UDPServer {

    public static final int PORT = 8888;

    public void start(){
        System.out.println("启动服务");
        //创建UDP服务端
        try {
            DatagramSocket server = new DatagramSocket(PORT);
            //接收数据报
            while(true) {
                byte[] buff = new byte[1024];
                DatagramPacket packet = new DatagramPacket(buff,0,buff.length);
                //将接收的数据放入数据报
                server.receive(packet);
                String msg = new String(packet.getData(),0,packet.getLength(),"UTF-8");
                System.out.println("接收到：" + msg);
            }
        } catch (SocketException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        new UDPServer().start();
    }

}

public class UDPClient {

    public void send(String ip,int port,String msg){
        //创建客户端
        try {
            DatagramSocket client = new DatagramSocket();
            //创建数据报
            byte[] buff = msg.getBytes();
            DatagramPacket packet = new DatagramPacket(buff,0,buff.length, InetAddress.getByName(ip),port);
            //发送数据报
            client.send(packet);
        } catch (SocketException | UnknownHostException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        new UDPClient().send("127.0.0.1",8888,"Hello UDP!!");
    }
}

?可以根据socket完成udp连续聊天。

总结

? ? ? ? 网络的七层模型

? ? ? ? TCP的三次握手和四次挥手

? ? ? ? SOCKET编程和UDP编程?