手写一个简单的Server和Client

package TCP;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;

public class Server {
private static ArrayList<String> list = new ArrayList<>();
 static {
    list.add("zzxkj");
    list.add("zxj");
}
public static void main(String[] args) {
    ServerSocket serverSocket;
    int port = 8080;
    System.out.println("默认端口：8080");
    try {
        //创建绑定到特定8080端口的服务器套接字
          serverSocket = new ServerSocket(port);
        //返回此套接字正在侦听的端口
          System.out.println("服务器正在监听的端口："+serverSocket.getLocalPort());
    while (true){
            try {
                //等待Client的TCP连接
           final Socket socket = serverSocket.accept();
                System.out.println("建立了与客户端的TCP连接，该客户端地址为：" + socket.getLocalSocketAddress() + socket.getLocalPort());
                service(socket);
            }catch (Exception e){
                System.out.println("与用户交互失败");
            }

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

}
/***响应***/
public static void service(Socket socket) throws Exception{
    /**读取请求信息**/
    InputStream in = socket.getInputStream();
    Thread.sleep(500);//线程休眠，等待Http请求
            int size = in.available();
    byte[] bytes = new byte[size];
    byte[] select = new byte[10];//用于判断该请求是登录，还是上传图片
           in.read(bytes);
    System.arraycopy(bytes,0,select,0,5);//因为设置Login为登录标志，即前缀，所以取前五个字节
           String prefix = new String(select).substring(0,5); //取前缀
           //System.out.println(prefix+" "+prefix.length());
    /**判断是上传图片还是请求登录，并发送响应结果**/
    OutputStream out= socket.getOutputStream();//将字节写入此套接字的输出流
           byte[] buffer = new byte[20];
    if(prefix.equals("Login")){
       // System.out.println(prefix);
        String s = new String(bytes);   //取完整信息
             String follow = s.substring(5); //取用户名
            //判断是否存在该用户
           if(list.contains(follow)){
            buffer = "欢迎光临".getBytes();
            System.out.println("登录成功");
        }else {
            buffer = "该用户不存在".getBytes();
            System.out.println("登录失败");
        }

    }
   else {
        String result = new String(bytes);
        System.out.println(result);//打印结果
                    buffer = "上传成功".getBytes();
    }
    out.write(buffer);
    Thread.sleep(1000);//线程休眠，等待HTTP得到响应
           socket.close();
 }
}

package TCP;

import java.io.InputStream;
import java.io.OutputStream;
import java.net.Socket;
import java.util.Scanner;

public class Client {
private static String host = "localhost";
private static int port = 8080;
private static String path = "XGZ.jpg";
private static String username="zzxkj";
public static void main(String[] args) {
    System.out.println("上传文件输入1，请求登录输入2");
    Scanner sc = new Scanner(System.in);
    int k=sc.nextInt();
    if(k==1) {
        System.out.println("请输入文件名称(示例：index.html)");
        path=sc.next();
        try {
            doPost(host,port,path);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    else{
        System.out.println("请输入用户名（示例：zzxkj）");
        username=sc.next();
        try {
            doLogin(host,port,username);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}
public static void doPost(String host , int port , String path) throws Exception{
    //建立一个TCP传输
            Socket socket = new Socket(host, port);
    InputStream in = Client.class.getResourceAsStream(path);
    int size = in.available();
    byte[] bytes = new byte[size];
    in.read(bytes);
    /**发送请求**/
    OutputStream out = socket.getOutputStream();
    out.write(bytes);
    //线程休眠等待响应结果
            Thread.sleep(2000);
    /**接收响应**/
    InputStream socketInputStream = socket.getInputStream();
    int length = socketInputStream.available();
    byte[] buffer = new byte[length];
    socketInputStream.read(buffer);
    String result = new String(buffer);
    System.out.println(result);
    socket.close();
}
public static void doLogin(String host , int port , String name) throws Exception{
    //建立一个TCP传输
            Socket socket = new Socket(host, port);
    StringBuilder stringBuilder = new StringBuilder("Login");
    stringBuilder.append(name);
    byte[] bytes = stringBuilder.toString().getBytes();
   /**发送请求**/
    OutputStream out = socket.getOutputStream();
    out.write(bytes);
    //线程休眠等待响应结果
           Thread.sleep(2000);
    /**接收响应**/
    InputStream socketInputStream = socket.getInputStream();
    int length = socketInputStream.available();
    byte[] buffer = new byte[length];
    socketInputStream.read(buffer);
    String result = new String(buffer);
    //打印结果
            System.out.println(result);
    socket.close();
 }
}