Java通过套接字传输多文件 [英] Java multiple file transfer over socket

问题描述

好的，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，因此只剩下文件，并通过同一个套接字一一传输.这里的arraylist 只填充了文件，没有目录.这里分别是客户端和服务器的接收和发送代码.代码运行良好，没有错误，除了所有数据都被写入第一个文件.后续文件在服务器文件夹中创建，但它们是 0 字节.任何输入将不胜感激.

Ok, trying to transfer a specified directory of files over a socket, remove the directory objects from the arraylist, so only files are left, and transfer them 1 by 1 over the same socket. The arraylist here is filled with ONLY files, no directories. Heres the receive and send code for the client and server respectively . The code runs fine without errors, except for ALL the data is being written to the first file. The subsequent files are created in the server folder, but they are 0 bytes. Any input would be greatly appreciated.

这是接收文件的服务器代码

THIS IS THE SERVER CODE FOR RECEIVING THE FILES

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();

    }


}

这是发送文件的客户端代码

THIS IS THE CLIENT CODE FOR SENDING THE FILES

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();
    }


}

推荐答案

您正在读取套接字，直到 read() 返回 -1.这是流结束条件 (EOS).EOS 在对等方关闭连接时发生.不是在写完一个文件时.

You are reading the socket until read() returns -1. This is the end-of-stream condition (EOS). EOS happens when the peer closes the connection. Not when it finishes writing one file.

您需要在每个文件之前发送文件大小.您已经对文件计数做了类似的事情.然后确保您为该文件读取了那么多字节:

You need to send the file size ahead of each file. You're already doing a similar thing with the file count. Then make sure you read exactly that many bytes for that file:

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，在发送数据之前，您当然必须在发送方调用 writeUTF(filename) 和 writeLong(filesize).

You can enclose all this in a loop that terminates when readUTF() throws EOFException. Conversely of course you have to call writeUTF(filename) and writeLong(filesize) at the sender, before sending the data.

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