java中的客户机/服务器：程序在输入第二个文件名时卡住

Question

我正在开发代码，将多个文件名发送到服务器端，然后确保服务器接收到这些内容并将其写入自己文件夹中的文件。当我输入第一个文件名时，它工作得很好，但当我输入第二个文件名时，代码就卡住了

这是我的客户代码：-

package fileTransfer;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.UnknownHostException;

public class EchoClient {

public static void main(String[] args) throws UnknownHostException {

    try {
        Socket clientSock=new Socket("localhost",8888);

        //to read from server
        BufferedReader br=new BufferedReader(new  InputStreamReader(clientSock.getInputStream())); //to read

        //to write to server
        PrintWriter pw=new PrintWriter(clientSock.getOutputStream(), true); 

        //for user input
        BufferedReader userIn=new BufferedReader(new InputStreamReader(System.in));
        BufferedReader fileContent=null;
        String str=null;
        String fileContentLine=null;
        while(true){
            if((str=br.readLine()).contains("file name")) //recieve echo from server
                System.out.println(str);


            str=userIn.readLine(); //read user input
            fileContent=new BufferedReader(new FileReader(str));
            pw.println(str);
            while((fileContentLine=fileContent.readLine()) != null){
                pw.println(fileContentLine);
            }

            while((str=br.readLine())!=null)
                System.out.println(str);

            pw.flush();

        }

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


}

}

这是我的服务器代码

package fileTransfer;

import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;

public class EchoServer {

 public static void main(String[] args){
    try {
        ServerSocket serverSock=new ServerSocket(8888);
        System.out.println("Waiting for client");
        Socket connectFromClient=serverSock.accept();

        File file=null;
        //reading data from client
        BufferedReader input=new BufferedReader(new InputStreamReader(connectFromClient.getInputStream()));

        //will write back to client
        PrintWriter pr=new PrintWriter(new OutputStreamWriter(connectFromClient.getOutputStream()));

        PrintWriter writeToFile=null;
        //sending following statements to client
        pr.println("Connection established with server! Give a file name");
        pr.flush();

        String response;

        while(true){

            while((response=input.readLine()) != null)
            {
            if(response==null)
                break;
            else{

            System.out.println(response);
            if(response.contains(".txt")){

                //file=new File("FromClient.txt");
                  file=new File("FromClient"+response);
                if(!file.exists())
                    file.createNewFile();
                writeToFile=new PrintWriter(file);
            }
            else{

                //writeToFile=new PrintWriter(file);
                writeToFile.println(response);
            }

            pr.println("Echo from server -> " + response);

            //System.out.println("Adding these contents to a file");
            writeToFile.flush();
            pr.flush();
            }
            }
        }


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


}

}

Answer 1

它在客户中陷入了这样的困境：

 while ((str = br.readLine()) != null) {
     System.out.println(str);
 }

等待更多服务器排队

您必须告诉客户端何时停止从套接字流读取文件数据，并跳转到下一个文件。例如，您可以在文件内容之前发送要传输的字节数，从流中读取该字节数，然后转到下一个文件

我把你的代码修改作为一个例子，作为我想表达的想法。 首先，我得到文件的总行号（我想是文本文件），然后将其发送到服务器，服务器知道在跳转到下一个文件之前要读取多少行。 例如，它可以更改为使用文件的总大小（以字节为单位）。 这个代码不是100%正确的，它是有效的，以它为例

客户：

    import java.io.BufferedReader;
    import java.io.FileReader;
    import java.io.IOException;
    import java.io.InputStreamReader;
    import java.io.PrintWriter;
    import java.net.Socket;
    import java.net.UnknownHostException;

    public class EchoClient {

        public static void main(final String[] args) throws UnknownHostException {

            try {
                final Socket clientSock = new Socket("localhost", 8888);

                // to read from server
                final BufferedReader br = new BufferedReader(new InputStreamReader(clientSock.getInputStream())); // to
                // read

                // to write to server
                final PrintWriter pw = new PrintWriter(clientSock.getOutputStream(), true);

                // for user input
                final BufferedReader userIn = new BufferedReader(new InputStreamReader(System.in));
                BufferedReader fileContent = null;
                String str = null;
                String fileContentLine = null;
                while (true) {
                    System.out.println("Print filename");
                    str = userIn.readLine(); // read user input
                    fileContent = new BufferedReader(new FileReader(str));
                    pw.println(str);
                    // first count the line number:
                    int lineno = 0;
                    while ((fileContentLine = fileContent.readLine()) != null) {
                        lineno++;
                    }
                    fileContent.close();
                    //
                    fileContent = new BufferedReader(new FileReader(str));
                    pw.println(String.valueOf(lineno));
                    while ((fileContentLine = fileContent.readLine()) != null) {
                        pw.println(fileContentLine);
                    }

                    for (int i = 0; i < lineno; i++) {
                        str = br.readLine();
                        System.out.println(str);
                    }

                    pw.flush();

                }

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

        }
    }

服务器：

    import java.io.BufferedReader;
    import java.io.File;
    import java.io.IOException;
    import java.io.InputStreamReader;
    import java.io.OutputStreamWriter;
    import java.io.PrintWriter;
    import java.net.ServerSocket;
    import java.net.Socket;

    public class EchoServer {

        public static void main(final String[] args) {
            try {
                final ServerSocket serverSock = new ServerSocket(8888);
                System.out.println("Waiting for client");
                final Socket connectFromClient = serverSock.accept();

                File file = null;
                // reading data from client
                final BufferedReader input = new BufferedReader(new InputStreamReader(connectFromClient.getInputStream()));

                // will write back to client
                final PrintWriter pr = new PrintWriter(new OutputStreamWriter(connectFromClient.getOutputStream()));

                PrintWriter writeToFile = null;
                // sending following statements to client
                pr.println("Connection established with server! Give a file name");
                pr.flush();

                String response;

                while (true) {
                    final String fileName = input.readLine();
                    file = new File("FromClient" + fileName);
                    if (!file.exists()) {
                        file.createNewFile();
                    }
                    writeToFile = new PrintWriter(file);
                    final String sLineNo = input.readLine();
                    final int lineno = Integer.parseInt(sLineNo);
                    for (int i = 0; i < lineno; i++) {
                        response = input.readLine();
                        System.out.println(response);

                        // writeToFile=new PrintWriter(file);
                        writeToFile.println(response);

                        pr.println("Echo from server -> " + response);

                        // System.out.println("Adding these contents to a file");
                        writeToFile.flush();
                        pr.flush();
                    }
                    writeToFile.close();
                }

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

        }
    }

我希望能有所帮助