Java 通过套接字传输多个文件

Question

好吧，尝试通过套接字传输指定目录的文件，从数组列表中删除目录对象，这样只剩下文件，然后通过同一个套接字将它们一一传输。这里的数组列表仅包含文件，没有目录。下面分别是客户端和服务器的接收和发送代码。除了所有数据都被写入第一个文件之外，代码运行良好，没有错误。后续文件将在服务器文件夹中创建，但它们是 0 字节。任何意见将不胜感激。

这是用于接收文件的服务器代码

public void receive(){


    try {
        DataInputStream dis = new DataInputStream(new BufferedInputStream(socket.getInputStream()));
        DataOutputStream dos = new DataOutputStream(new BufferedOutputStream(socket.getOutputStream()));
//read the number of files from the client
        int number = dis.readInt();
        ArrayList<File>files = new ArrayList<File>(number);
        System.out.println("Number of Files to be received: " +number);
        //read file names, add files to arraylist
        for(int i = 0; i< number;i++){
            File file = new File(dis.readUTF());
            files.add(file);
        }
        int n = 0;
        byte[]buf = new byte[4092];

        //outer loop, executes one for each file
        for(int i = 0; i < files.size();i++){

            System.out.println("Receiving file: " + files.get(i).getName());
            //create a new fileoutputstream for each new file
            FileOutputStream fos = new FileOutputStream("C:\\users\\tom5\\desktop\\salestools\\" +files.get(i).getName());
            //read file
            while((n = dis.read(buf)) != -1){
                fos.write(buf,0,n);
                fos.flush();
            }
            fos.close();
        }

    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();

    }


}

这是用于发送文件的客户端代码

public void send(ArrayList<File>files){

    try {
        DataInputStream dis = new DataInputStream(new BufferedInputStream(socket.getInputStream()));
        DataOutputStream dos = new DataOutputStream(new BufferedOutputStream(socket.getOutputStream()));
        System.out.println(files.size());
//write the number of files to the server
        dos.writeInt(files.size());
        dos.flush();

        //write file names 
        for(int i = 0 ; i < files.size();i++){
            dos.writeUTF(files.get(i).getName());
            dos.flush();
        }

        //buffer for file writing, to declare inside or outside loop?
        int n = 0;
        byte[]buf = new byte[4092];
        //outer loop, executes one for each file
        for(int i =0; i < files.size(); i++){

            System.out.println(files.get(i).getName());
            //create new fileinputstream for each file
            FileInputStream fis = new FileInputStream(files.get(i));

            //write file to dos
            while((n =fis.read(buf)) != -1){
                dos.write(buf,0,n);
                dos.flush();

            }
            //should i close the dataoutputstream here and make a new one each time?
        }
        //or is this good?
        dos.close();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }


}

Answer 1

您正在读取套接字，直到 read() 返回 -1。这是流结束条件 (EOS)。当对等方关闭连接时，就会发生 EOS。不是在它完成写入一个文件时。

您需要在每个文件之前发送文件大小。您已经对文件计数执行了类似的操作。然后确保您准确地读取了该文件的字节数:

String filename = dis.readUTF();
long fileSize = dis.readLong();
FileOutputStream fos = new FileOutputStream(filename);
while (fileSize > 0 && (n = dis.read(buf, 0, (int)Math.min(buf.length, fileSize))) != -1)
{
  fos.write(buf,0,n);
  fileSize -= n;
}
fos.close();

您可以将所有这些包含在一个循环中，该循环在 readUTF() 抛出 EOFException 时终止。相反，当然，在发送数据之前，您必须在发送方调用 writeUTF(filename) 和 writeLong(filesize) 。