java - 客户端/服务器程序之间的通信停止(java)

Question

我试图让客户端与java中的服务器进行通信，客户端只需发送想要搜索的文件的名称，服务器应该回答他的文件夹中是否存在。这是我写的代码。

客户端.java

import java.io.*;
import java.net.*;
import java.util.concurrent.*;

public class client{
    public static void main(String args[]) throws IOException, NumberFormatException, InterruptedException{
        Socket client_socket = new Socket(args[0], Integer.parseInt(args[1])); 
        System.out.println("connected\n");


        BufferedWriter netOut = new BufferedWriter(new OutputStreamWriter(client_socket.getOutputStream(), "UTF-8"));
        BufferedReader netIn = new BufferedReader(new InputStreamReader(client_socket.getInputStream(), "UTF-8"));

        netOut.write(args[2]);
        netOut.flush();

        String exist = netIn.readLine();

        System.out.println("The file you searched"+ exist);


        client_socket.close();
    }
}

args[0] 应该用作本地主机，args[1] 用作端口，args[2] 用作要搜索的文件的名称。

服务器.java

import java.io.*;
import java.net.*;
import java.util.concurrent.*;

public class server{
    public static void main(String args[]) throws IOException, InterruptedException{

        ServerSocket sock_server = new ServerSocket(Integer.parseInt(args[0]));

        while(true){
            Socket communication = sock_server.accept();
            System.out.println("connected!\n");

            BufferedWriter netOut = new BufferedWriter(new OutputStreamWriter(communication.getOutputStream(), "UTF-8"));
            BufferedReader netIn = new BufferedReader(new InputStreamReader(communication.getInputStream(), "UTF-8"));

            String fileName = new String();
            fileName = netIn.readLine();

            System.out.println("The name of the file is"+fileName);

            File tempFile = new File(fileName);
            boolean exists = tempFile.exists();
            System.out.println(exists);
            if(exists){
                netOut.write("The file do exists");
                netOut.flush();
            } else {
                netOut.write("The file doesn't exist");
                netOut.flush();
            }


            communication.close();
        }    
    }
} 

arg[0] = 通信端口

发生的情况是服务器永远不会发送证明文件存在的字符串。我在服务器中添加了一些 println() 以确保从客户端到服务器的通信正常，并且看起来工作正常。

Answer 1

不知道为什么它在你的情况下不起作用，但你可以尝试在这种情况下使用ObjectInputStream和ObjectOutputStream，我发现这非常有用。我测试了它并且可以很好地与您的代码配合使用。因此，在客户端，您可以使用以下内容:

...
ObjectOutputStream netOut = new ObjectOutputStream(client_socket.getOutputStream());
ObjectInputStream netIn = new ObjectInputStream(client_socket.getInputStream());
netOut.writeObject("a_file_name");
netOut.flush();
String exist = (String)netIn.readObject();
…

服务器端也类似:

…
ObjectOutputStream netOut = new ObjectOutputStream(communication.getOutputStream());
ObjectInputStream netIn = new ObjectInputStream(communication.getInputStream());
String fileName = new String();
fileName = (String)netIn.readObject();
…
if(exists){
      netOut.writeObject("The file do exists");
      netOut.flush();
} else {
      netOut.writeObject("The file doesn't exist");
      netOut.flush();
}

由于涉及转换，请确保您还捕获或声明 ClassNotFoundException