Question

我无法弄清楚原因。当服务器向客户端发送字符串时，客户端就可以正常运行。但是当我向我的Client类添加代码以将字符串发送到我的服务器时，它不起作用。帮助

编辑：所以我删除了out.close（）;在我的Server类中，并用skt.shutdownOutput（）替换它;但现在，当我打电话给我的课程时，我得到了：

======================
Server has connected!
Server: Sending message: Test string to show connection between server and client.
Client: Received message: null
Server: Received message: null

为什么？

客户类：

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

class Client {

public static void main(String args[]) {

}

//for receiving messages from Server

public void receiveMessage() {
    try {
        Socket skt = new Socket(InetAddress.getLocalHost().getHostName(), 1234);
        BufferedReader in = new BufferedReader(new InputStreamReader(skt.getInputStream()));
        //while (!in.ready()) {}
        System.out.println("Client: Received message: " + in.readLine()); // Read one line and output it
        in.close();
        //skt.close(); //maybe delete
    } catch (Exception e) {
        System.out.print("Client had error receiving message.\n");
    }
}

//for sending messages to Server
public void sendMessage(String message) throws IOException {
    try {
        Socket skt = new Socket(InetAddress.getLocalHost().getHostName(), 1234);
        PrintWriter pw = new PrintWriter(skt.getOutputStream());
        System.out.println("Client: Sending message: " + message);
        pw.print(message);
        //skt.close(); //maybe delete
    } catch (Exception e) {
        System.out.println(e);
        System.out.print("Client had error sending message.\n");
    }

}
}

服务器类：

import java.lang.*;
import java.io.*;
import java.net.*;
import java.util.concurrent.*;
import java.util.logging.Level;
import java.util.logging.Logger;

public class Server {

String message = "Test string to show connection between server and client.";

public void Open() {
    final ExecutorService clientProcessingPool = Executors.newFixedThreadPool(10);
    Runnable serverTask = new Runnable() {

        @Override
        public void run() {
            try {
                System.out.println("Opening...");
                ServerSocket srvr = new ServerSocket(1234);
                while (true) {
                    Socket skt = srvr.accept();
                    clientProcessingPool.submit(new ClientTask(skt));
                }
            } catch (Exception e) {
                System.out.println(e);
                System.out.print("You're opening too many servers in the same location, fool!\n");
            }
        }
    };
    Thread serverThread = new Thread(serverTask);
    serverThread.start();
}

private class ClientTask implements Runnable {

    private final Socket skt;

    private ClientTask(Socket skt) {
        this.skt = skt;
    }

    @Override
    public void run() {
        //for sending messages
        System.out.println("======================");
        System.out.println("Server has connected!");
        PrintWriter out = null;
        try {
            out = new PrintWriter(skt.getOutputStream(), true);
        } catch (IOException ex) {
            System.out.println(ex);
            System.out.println("Server had error sending message.");
        }
        System.out.print("Server: Sending message: " + message + "\n");
        out.print(message);
        //out.close();
        try {
            skt.shutdownOutput();
        } catch (IOException ex) {
            Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
        }

        /*
        try {
            skt.close();
        } catch (IOException ex) {
            Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
        }*/

        //for receiving messages
        //maybe make message procesing method
        try {
            BufferedReader br = new BufferedReader(new InputStreamReader(skt.getInputStream()));
            System.out.println("Server: Received message: " + br.readLine()); // Read one line and output it
            //br.close();
            //skt.close(); //maybe delete
        } catch (Exception e) {
            System.out.println("Server had error receiving message.");
            System.out.println("Error: " + e);
        }

    }
}

}

感谢您的任何建议。

Answer 1

    out.print(message);
    out.close();

关闭PrintStream后，您将关闭基础OutputStream。

getOutputStream()中Socket的文档说：

关闭返回的OutputStream将关闭相关的套接字。

因此，当您关闭PrintStream时，也会关闭套接字。仅当您完成当前会话的客户端和服务器之间的所有通信时才关闭流。

您的下一个问题（编辑后）是您没有刷新数据。您的客户端连接，服务器打印，无需刷新，因此数据仍在缓冲区中等待，而不是在流中。像以前一样关闭流也会刷新数据，但是现在您只是将流丢弃，未被刷新的数据将被丢弃。

因此，流关闭，客户端看到指示流结束的null。

因此，您需要在丢弃流之前刷新数据。

并且服务器报告它已收到null，因为在其输入流上没有发送任何内容。客户端接收信息然后退出，这会导致套接字关闭，流关闭，服务器看到流末尾。

如果您拨打sendMessage方法，您会看到几乎相同的内容。流正在写一些东西，但没有人在听它。由于消息很短，服务器不会阻止写入，但没有人在另一侧读取它，它有可能阻止。然后，服务器尝试读取发送给它的内容。但是您的客户端在完成执行并关闭套接字之前不会刷新数据。因此，服务器也会看到null。

获取＆＃34;错误：java.net.SocketException：Socket已关闭＆＃34;尝试从我的客户端类发送消息到我的服务器类时

1 个答案: