实验十六 Socket通信

一、实验预热
1、请简单解释网络三要素都是什么，分别有什么作用。
IP地址：唯一标识网络上的每一台计算机
端口号：设备与外界通讯交流的出入口
协议：通信计算机双方必须共同遵从的一组约定

2、请描述Socket通信的一般流程。
首先Socket是网络驱动层提供给应用程序的接口，即通过Socket把数据从应用层封装到数据链路层，反之通过Socket可以解封我们的数据

3、请说明TCP和UDP传输的区别。
TCP：面向连接、传输可靠（保证数据正确性、保证数据顺序）、用于传输大量数据（流模式）、速度慢、建立连接需要开销较多（时间、系统资源）
UDP：面向非连接、传输不可靠、用于传输少量数据（数据包模式）、速度快

二、实验内容
1、使用Socket编程实现基于TCP的多客户端用户登录。
代码：
服务器端：

package leif.tests.socket;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.Socket;

public class Server {
    public static void main(String[] args) {
        // 创建一个服务器端Socket，即ServerSocket
        ServerSocket serverSocket = null;

        try {
            // 指定绑定的端口，并监听此端口
            serverSocket = new ServerSocket(8888);
            Socket socket = null;
            // 记录客户端的数量
            int count = 0;
            System.out.println("服务器即将启动，等待客户端连接");

            // 循环监听等待客户端连接
            while (true) {
                // 调用accept()方法开始监听，等待客户端连接
                socket = serverSocket.accept();
                // 创建一个新的线程
                ServerThread serverThread = new ServerThread(socket);
                // 启动线程
                serverThread.start();
                // 统计客户端的数量
                count++;
                System.out.println("客户端数量：" + count);
                InetAddress inetAddress = socket.getInetAddress();
                System.out.println("当前客户端IP：" + inetAddress.getHostAddress());
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (serverSocket != null) {
                    serverSocket.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

class ServerThread extends Thread {
    // 和本线程相关的Socket
    private Socket socket;

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

    // 线程执行的操作，响应客户端的请求
    @Override
    public void run() {
        InputStream inputStream = null;
        InputStreamReader inputStreamReader = null;
        BufferedReader bufferedReader = null;
        OutputStream outputStream = null;
        PrintWriter printWriter = null;

        try {
            // 获取一个输入流，并读取客户端的信息
            inputStream = socket.getInputStream();
            // 将字节流转化为字符流
            inputStreamReader = new InputStreamReader(inputStream);
            // 添加缓冲
            bufferedReader = new BufferedReader(inputStreamReader);
            String info = null;

            // 循环读取数据
            while ((info = bufferedReader.readLine()) != null) {
                System.out.println("我是服务器，客户端说：" + info);
            }

            // 关闭输入流
            socket.shutdownInput();
            // 获取输出流，响应客户端的请求
            outputStream = socket.getOutputStream();
            // 将输出流包装为打印流
            printWriter = new PrintWriter(outputStream);
            printWriter.write("欢迎你");
            // 将缓存输出
            printWriter.flush();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            // 关闭资源
            try {
                if (printWriter != null) {
                    printWriter.close();
                }

                if (outputStream != null) {
                    outputStream.close();
                }

                if (bufferedReader != null) {
                    bufferedReader.close();
                }

                if (inputStreamReader != null) {
                    inputStreamReader.close();
                }

                if (inputStream != null) {
                    inputStream.close();
                }

                if (socket != null) {
                    socket.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

客户端1：

package leif.tests.socket;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.Socket;

public class Client1 {
    public static void main(String[] args) {
        Socket socket = null;
        PrintWriter printWriter = null;
        OutputStream outputStream = null;
        InputStream inputStream = null;
        InputStreamReader inputStreamReader = null;
        BufferedReader bufferedReader = null;

        try {
            // 创建客户端Socket，指定服务器端口号和地址
            socket = new Socket("localhost", 8888);
            // 获取输出流，向服务器发送信息
            outputStream = socket.getOutputStream();
            // 将输出流包装为打印流
            printWriter = new PrintWriter(outputStream);
            printWriter.write("用户名：lbc，密码：123");
            printWriter.flush();
            socket.shutdownOutput();
            inputStream = socket.getInputStream();
            inputStreamReader = new InputStreamReader(inputStream);
            bufferedReader = new BufferedReader(inputStreamReader);
            String info = null;

            // 循环读取
            while ((info = bufferedReader.readLine()) != null) {
                System.out.println("我是客户端1，服务器说：" + info);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            // 关闭资源
            try {
                if (bufferedReader != null) {
                    bufferedReader.close();
                }

                if (inputStreamReader != null) {
                    inputStreamReader.close();
                }

                if (inputStream != null) {
                    inputStream.close();
                }

                if (printWriter != null) {
                    printWriter.close();
                }

                if (outputStream != null) {
                    outputStream.close();
                }

                if (socket != null) {
                    socket.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

客户端2：

package leif.tests.socket;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.Socket;

public class Client2 {
    public static void main(String[] args) {
        Socket socket = null;
        PrintWriter printWriter = null;
        OutputStream outputStream = null;
        InputStream inputStream = null;
        InputStreamReader inputStreamReader = null;
        BufferedReader bufferedReader = null;

        try {
            // 创建客户端Socket，指定服务器端口号和地址
            socket = new Socket("localhost", 8888);
            // 获取输出流，向服务器发送信息
            outputStream = socket.getOutputStream();
            // 将输出流包装为打印流
            printWriter = new PrintWriter(outputStream);
            printWriter.write("用户名：gll，密码：123");
            printWriter.flush();
            socket.shutdownOutput();
            inputStream = socket.getInputStream();
            inputStreamReader = new InputStreamReader(inputStream);
            bufferedReader = new BufferedReader(inputStreamReader);
            String info = null;

            // 循环读取
            while ((info = bufferedReader.readLine()) != null) {
                System.out.println("我是客户端2，服务器说：" + info);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            // 关闭资源
            try {
                if (bufferedReader != null) {
                    bufferedReader.close();
                }

                if (inputStreamReader != null) {
                    inputStreamReader.close();
                }

                if (inputStream != null) {
                    inputStream.close();
                }

                if (printWriter != null) {
                    printWriter.close();
                }

                if (outputStream != null) {
                    outputStream.close();
                }

                if (socket != null) {
                    socket.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

结果截图：

image.png

2、使用Socket实现基于UDP传输的客户咨询功能，要求接收方显示内容如下格式。

image.png

代码：
服务器端：

package leif.tests.socket;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;
import java.util.Scanner;

public class Server {
    public static void main(String[] args) {
        DatagramSocket datagramSocket = null;
        Scanner scanner = null;

        try {
            // 接收数据
            datagramSocket = new DatagramSocket(8648);
            byte receiveData[] = new byte[4 * 1024];
            // 两个参数：byte数组、数组长度
            DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
            datagramSocket.receive(receivePacket);
            // 三个参数：包、包的起始位置、包的大小
            String result = new String(receivePacket.getData(), receivePacket.getOffset(), receivePacket.getLength());
            System.out.println("客户端（" + receivePacket.getAddress().toString() + "）：" + result);
            // 发送数据
            scanner = new Scanner(System.in);
            System.out.print("我说：");
            String string = scanner.next();
            byte sendData[] = string.getBytes();
            // 四个参数：byte数组、数组长度、发送的地址、发送的端口号
            DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, receivePacket.getAddress(), receivePacket.getPort());
            datagramSocket.send(sendPacket);
        } catch (SocketException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (scanner != null) {
                scanner.close();
            }

            if (datagramSocket != null) {
                datagramSocket.close();
            }
        }
    }
}

客户端：

package leif.tests.socket;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;
import java.net.UnknownHostException;
import java.util.Scanner;

public class Client {
    public static void main(String[] args) {
        DatagramSocket datagramSocket = null;
        Scanner scanner = null;
        try {
            datagramSocket = new DatagramSocket(5548);
            InetAddress inetAddress = InetAddress.getLocalHost();
            scanner = new Scanner(System.in);
            System.out.print("我说：");
            String string = scanner.next();
            byte[] sendData = string.getBytes();
            DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, inetAddress, 8648);
            datagramSocket.send(sendPacket);
            byte receiveData[] = new byte[4 * 1024];
            DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
            datagramSocket.receive(receivePacket);
            String result = new String(receivePacket.getData(), receivePacket.getOffset(), receivePacket.getLength());
            System.out.println("服务器说：" + result);
        } catch (SocketException e) {
            e.printStackTrace();
        } catch (UnknownHostException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (scanner != null) {
                scanner.close();
            }

            if (datagramSocket != null) {
                datagramSocket.close();
            }
        }
    }
}

结果截图：

image.png

实验十六 Socket通信

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