public void run(){ PrintWriter pw = null; try { InputStream in = socket.getInputStream(); InputStreamReader isr = new InputStreamReader(in, "utf-8"); BufferedReader br = new BufferedReader(isr); OutputStream out = socket.getOutputStream(); OutputStreamWriter osw = new OutputStreamWriter(out, "utf-8"); BufferedWriter bw = new BufferedWriter(osw); pw = new PrintWriter(bw, true); synchronized (Server.this){//限制自身 map.put(host,pw); pws = Arrays.copyOf(pws,pws.length+1); pws[pws.length-1] = pw; } send(host+"上线了，当前在线人数："+pws.length);

这段代码是一个多线程聊天室服务器端的run()方法。首先，创建一个PrintWriter对象pw，用于向客户端发送消息。接着，通过socket.getInputStream()获取输入流，通过InputStreamReader将字节流转化为字符流，并指定字符编码为"utf-8"。再通过BufferedReader对字符流进行缓冲读取。同时，通过socket.getOutputStream()获取输出流，通过OutputStreamWriter将字符流转化为字节流，并指定字符编码为"utf-8"。再通过BufferedWriter对字节流进行缓冲写入。最后，通过PrintWriter将字符流转换为字节流，并自动刷新缓冲区，发送消息给客户端。在synchronized块中，将当前客户端的输出流pw存入map集合中，方便后面广播消息使用。同时，将pws数组扩容，并将当前客户端的输出流pw存入pws数组中。最后，向所有客户端发送上线消息及当前在线人数。

相关问题

利用Java1.实现daytime协议，从远程计算机上获取时间，并更新本机时间。 2.实现echo协议，向远程计算机发送信息，并获取返回信息。

1. 实现daytime协议：

import java.io.*;
import java.net.*;

public class DaytimeClient {
    public static void main(String[] args) {
        try {
            // 创建连接
            Socket socket = new Socket("time.nist.gov", 13);
            InputStream is = socket.getInputStream();
            InputStreamReader isr = new InputStreamReader(is);
            BufferedReader br = new BufferedReader(isr);

            // 读取时间信息
            String time = br.readLine();

            // 解析时间信息
            String[] tokens = time.split(" ");
            String dateTime = tokens[2] + " " + tokens[3];

            // 设置本机时间
            Runtime.getRuntime().exec("cmd /c time " + dateTime);

            // 关闭连接
            br.close();
            isr.close();
            is.close();
            socket.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

2. 实现echo协议：

import java.io.*;
import java.net.*;

public class EchoClient {
    public static void main(String[] args) {
        try {
            // 创建连接
            Socket socket = new Socket("localhost", 7777);
            BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
            PrintWriter pw = new PrintWriter(socket.getOutputStream(), true);
            BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));

            // 发送消息并接收回复
            String line;
            while ((line = br.readLine()) != null) {
                pw.println(line);
                System.out.println("Server response: " + in.readLine());
            }

            // 关闭连接
            br.close();
            pw.close();
            in.close();
            socket.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

服务端代码：

import java.io.*;
import java.net.*;

public class EchoServer {
    public static void main(String[] args) {
        try {
            // 创建ServerSocket，监听端口7777
            ServerSocket serverSocket = new ServerSocket(7777);
            while (true) {
                // 等待客户端连接
                Socket socket = serverSocket.accept();
                System.out.println("Client connected: " + socket.getInetAddress().getHostAddress());
                BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
                PrintWriter out = new PrintWriter(socket.getOutputStream(), true);

                // 接收消息并回复
                String line;
                while ((line = in.readLine()) != null) {
                    System.out.println("Received message: " + line);
                    out.println("Echo: " + line);
                }

                // 关闭连接
                in.close();
                out.close();
                socket.close();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}