Question

我在TFTP服务器上工作。根据图像，我的数据包的最大长度是516字节（2 + 2 + 512）。

我正在尝试从客户端datagrampacket获取原始长度（在这种情况下，在RRQ数据包中发送13个字节），而不是获取服务器datagrampacket长度（516字节），我保存客户端datagrampacket。

我需要提取文件名，我这样做但是字符串内容是“filename + nullBytes”，那些空字节来自服务器datagrampacket。

这是我陷入困境的代码：

public static short RRQ = 1;
        enter code here
    public void dataMetod() throws IOException{
                        byte[] packet = new byte[516];
                        //socket with listening port 5000
                        DatagramSocket datagramSocket = new DatagramSocket(5000);

                    //while receive packets
                    while (true) {
                    DatagramPacket datagramPacket = new  DatagramPacket(packet,packet.length);
                    datagramSocket.receive(datagramPacket);
                    System.out.println("server: new packet!!:");

                    //create a byte[] with the "received packet length"(that's not true)
                    byte[] inData = new byte[datagramPacket.getLength()];
                    inData = datagramPacket.getData();

                    System.out.println("length: "+inData.length);
                    byte code;
                    code = inData[1];
                    System.out.println(code);

                    //check if its an RRQ packet
                    if (code == RRQ) {
                        System.out.println("server: RRQ PACKET!!");
                        String fileName = this.getFileName(inData);
                        System.out.println(fileName);


                }

public String getFileName(byte[] inData) {
        byte[] aux = new byte[inData.length - 7];
        for (int i = 0; i < aux.length; i++) {
            aux[i] = inData[i + 2];
        }
        return new String(aux);
    }

http://i.stack.imgur.com/6dTH6.png

Answer 1

试试这个：

public String getFileName(byte[] inData) {

    final int maxLen = inData.length;

    final StringBuilder sb = new StringBuilder();

    int i = 2;
    byte b;

    while ( (i < maxLen) && (b = inData[i]) != 0 ) {
        final int v = ((int)b) & 0xff;
        sb.append( (char) v );
        i++;
    }
    return sb.toString();
}

Answer 2

我们可以通过在客户端类的fileName字符串中添加“\ n”，而不是获取接收数据包的原始长度（通过数组搜索文件名），然后使用BufferedReader来检测“\ n “并保存fileName。代码：

    public String getFileName(byte[] inData) throws IOException {

    //get a sub-array, from index[2] (beacuse we dont want opCode) to inData length

        byte[] b =Arrays.copyOfRange(inData, 2, inData.length);

        InputStream is = new ByteArrayInputStream(b);
        BufferedReader bf = new BufferedReader(new InputStreamReader(is));

    //We read a word that will be saved when "\n" is found.
    //(adding "\n" previously to the fileName String in client class)

        String filename = bf.readLine();
        bf.close();
        is.close();
        System.out.println("server: filename is: "+filename.length()+" bytes");
        return filename;
}

如何从RRQ datagramPacket获取文件名？

2 个答案: