为什么在Java TCP中发送数据时套接字总是关闭

Question

服务器类：该程序即将从客户端接收数据，然后进行回复。 服务器正常...但是问题是服务器将答复发送给客户端时。 客户总是说“套接字关闭”。 我尝试删除secket close语句，但结果是相同的..，输出显示“套接字已关闭”。 所以请帮我解决这个问题...

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintStream;
import java.net.BindException;
import java.net.ServerSocket;
import java.net.Socket;

 public class Nomor3Server {

    public static final int SERVICE_PORT = 2020;

public static void main(String[] args) {
    try {
        ServerSocket server = new ServerSocket(SERVICE_PORT);
        System.out.println("DAytime service started");

        for (;;) {
            Socket nextClient = server.accept();

            BufferedReader pesan = new BufferedReader(new InputStreamReader(nextClient.getInputStream()));
            String messageIn = pesan.readLine();
            System.out.println("Received request from "
                    + nextClient.getInetAddress() + " : "
                    + nextClient.getPort()
                    + "\nIsi Pesan : " + messageIn);
            String messageOut = "انا لا ادر";

            switch (messageIn) {
                case "saya":
                    messageOut = "أنا";
                    break;
                case "kamu":
                    messageOut = "أنت";
                    break;
                default:
                    break;

            }

            OutputStream out = nextClient.getOutputStream();
            PrintStream pout = new PrintStream(out);

            pout.print(messageOut);

            out.flush();
            out.close();
            System.out.println("Message sent");
            //nextClient.close();
        }
    } catch (BindException e) {
        System.err.println("Server Already Running on port : " + SERVICE_PORT);
    } catch (IOException ioe) {
        System.err.println("error : " + ioe);

    }
}

}

客户类别：

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintStream;
import java.net.Socket;


public class Nomor3Client {

    public static final int SERVICE_PORT = 2020;

public static void main(String[] args) {
    try {
        String hostname = "localhost";

        System.out.println("Connection Established");

        //for (;;) {

            System.out.println("Enter Your Message : ");
            BufferedReader read = new BufferedReader(new InputStreamReader(System.in));
            String pesan = read.readLine();
            Socket daytime = new Socket(hostname, SERVICE_PORT);

            if (pesan.equals("exit")) {
                System.exit(0);
            } else {

                daytime.setSoTimeout(2000);

                OutputStream out = daytime.getOutputStream();
                PrintStream pout = new PrintStream(out);

                pout.print(pesan);

                out.flush();
                out.close();



                BufferedReader messageIn = new BufferedReader(new InputStreamReader(daytime.getInputStream()));
                System.out.println("Respond : " + messageIn.readLine());
                System.out.println("diterima");


            }


            daytime.close();
        //}

    } catch (IOException e) {
        System.err.println("Error : " + e);
    }
}

}

Answer 1

            OutputStream out = daytime.getOutputStream();
            PrintStream pout = new PrintStream(out);

            pout.print(pesan);

            out.flush();
            out.close();

https://docs.oracle.com/javase/7/docs/api/java/net/Socket.html#getOutputStream（）

关闭返回的OutputStream将关闭关联的套接字。

Answer 2

在以下情况下，套接字会关闭：

• 当您关闭插座时，
• 当您关闭输入或输出套接字流时，
• 关闭对象时，该对象将直接或间接包装输入或输出套接字流，例如BufferedReader或Scanner 。

Answer 3

服务器等级

            OutputStream out = nextClient.getOutputStream();
            PrintStream pout = new PrintStream(out);

            pout.print(messageOut);

            out.flush();
            out.close(); //Don't close this

客户代码：

OutputStream out = daytime.getOutputStream();
PrintStream pout = new PrintStream(out);

pout.print(pesan);

out.flush();
out.close(); //Don't close this