Thread: TFTP Server not allowing data transfer

Hi all, my TFTP server I want to use as a template will not alllow me to send or recieve data. Any advice would be great as I don't know if its possibly a folder access problem on my PC. Here is the code:

public class TFTPS {
 
    /**
     * @param args the command line arguments
     */
 
        // TODO code application logic here
     public static final int tftpRRQ=1;
 	  public static final int tftpWRQ=2;
	  public static final int tftpDATA=3;
	  public static final int tftpACK=4;
	  public static final int tftpERROR=5;
 
	  public static final int maxTftpPakLen=516;
 
	  public static void main(String argv[]) {
              int port = 69;
	    try {
	      DatagramSocket sock = new DatagramSocket(port);
	      System.out.println("Server Ready.  Listening on port:  "+sock.getLocalPort());
 
	      for(;;) {
	        UdpData reqData = new UdpData(maxTftpPakLen);
	        DatagramPacket reqPak = reqData.mkPacket();
 
	        sock.receive(reqPak);
 
	        if (reqData.getInt(0)==tftpRRQ) {
	          System.out.println("Request from "+reqPak.getAddress());
	          tftpTransfer t = new tftpTransfer(reqPak);
	        }
	      }
	    }
	    catch(Exception e) { System.out.println("Server terminated"); }
	  }
	}

class UdpData {
 
private byte data[];
 
 	  public UdpData(int len) { data = new byte[len]; };
 		  public UdpData(DatagramPacket pack) { data = pack.getData(); }
 
	  public byte[] getData() { return data; };
 
	  public int length() { return data.length; };
 
	  public DatagramPacket mkPacket() { return new DatagramPacket(data,data.length); };
 
	  public DatagramPacket mkPacket(int len) { return new DatagramPacket(data,len); };
 
	  public DatagramPacket mkPacket(InetAddress dest, int port) {
	    return new DatagramPacket(data,data.length,dest,port);
	  };
 
	  public DatagramPacket mkPacket(InetAddress dest, int port, int len) {
	    return new DatagramPacket(data,len,dest,port);
	  };
 
	  public int getInt(int offset) {
 
	    // Fix to avoid sign extension
 
	    // Remember what the MSB is and then turn it off to avoid sign extension.  It is
	    // then added back to the sum after everything has been converted to integers.
 
	    byte lo = data[offset+1];
	    int signBit = (int)(lo&0x80);
	    lo&=0x7f;
 
	    // Standard TCP/IP byte order is hiByte followed by loByte (big endian)
 
	    int hiByte = (int)data[offset];
	    int loByte = (int)lo;
 
	    return (hiByte<<8)+signBit+loByte;
	  };
 
	  public void putInt(int val, int offset) {
	    int loByte = val%256;
	    int hiByte = val>>>8;
 
	    // Standard TCP/IP byte order is hiByte followed by loByte (big endian)
 
	    data[offset] = (byte)hiByte;
	    data[offset+1] = (byte)loByte;
	  };
 
	  public String getString(int offset) {
	    StringBuffer strBuf = new StringBuffer();
	    int curPos = offset;
 
	    while (data[curPos]!=0) {
	      strBuf.append((char)data[curPos]);
	      curPos++;
	    }
 
	    return new String(strBuf);
	  };
 
	  public void putString(String str, int offset) {
	    str.getBytes(0,str.length(),data,offset);
	    data[offset+str.length()]=0;
	  };
	}

class tftpTransfer {
 
protected DatagramSocket sock;
     protected InetAddress clientIP;
    protected int clientPort;
    protected FileInputStream source;
    protected UdpData dataPak;
 
    public tftpTransfer(DatagramPacket reqPak) {
      try {
        sock = new DatagramSocket();
 
        clientIP = reqPak.getAddress();
       clientPort = reqPak.getPort();
 
        UdpData reqData = new UdpData(reqPak);
 
        File srcFile = new File(reqData.getString(2));
 
        if (srcFile.exists() && srcFile.isFile() && srcFile.canRead()) {
          source = new FileInputStream(srcFile);
          dataPak = new UdpData(516);                             // 516==max pak len
          dataPak.putInt(3,0);                                    // 3==DATA opcode
 
          this.start();     //This also seems to be an isssue
        }
      } catch (Exception e) { System.out.println("Client failed"); };
    }
 
    public void run() {
      int bytesRead = 512;
      DatagramPacket ack = new DatagramPacket(new byte[4],4);
 
      try {
        for (int blkNum=0; bytesRead==512; blkNum++) {            // 512==max data len
          dataPak.putInt(blkNum,2);
          bytesRead = source.read(dataPak.getData(),4,512);
          sock.send(dataPak.mkPacket(clientIP,clientPort,516));   // 516==max data len + header
 
          sock.receive(ack);
        }
      } catch (Exception e) { System.out.println("Client failed"); }
 
      try {
        source.close();
        sock.close();
      } catch (Exception e) {};
    }
}

I have had a few late nights (5am) trying to solve this, to no avail so I have decided to seek advice.

I have used WireShark while connecting with a client but all it shows is the client requesting a "Write Request", the server just does not respond, resulting in the client timing out. The server and WireShark report no errors. I have tried debugging, but this was little help as I have not used this tool very much. I just did some print lines and it seems to be a problem with the tftpTransfer class. Thanks for that advice.

Did some more debugging the server is getting to here:

public int getInt(int offset) {
	System.out.println("Getting to GetInt");
	    // Fix to avoid sign extension
 
	    // Remember what the MSB is and then turn it off to avoid sign extension.  It is
	    // then added back to the sum after everything has been converted to integers.
 
	    byte lo = data[offset+1];
	    int signBit = (int)(lo&0x80);
	    lo&=0x7f;
 
	    // Standard TCP/IP byte order is hiByte followed by loByte (big endian)
 
	    int hiByte = (int)data[offset];
	    int loByte = (int)lo;
 
	    return (hiByte<<8)+signBit+loByte;
	  };
 
	  public void putInt(int val, int offset) {
	    int loByte = val%256;
	    int hiByte = val>>>8;
 
	    // Standard TCP/IP byte order is hiByte followed by loByte (big endian)
 
	    data[offset] = (byte)hiByte;
	    data[offset+1] = (byte)loByte;
	  };
 
	  public String getString(int offset) {
	    StringBuffer strBuf = new StringBuffer();
	    int curPos = offset;
 
	    while (data[curPos]!=0) {
	      strBuf.append((char)data[curPos]);
	      curPos++;
	    }
 
	    return new String(strBuf);
	  };
 
	  public void putString(String str, int offset) {
	    str.getBytes(0,str.length(),data,offset);
	    data[offset+str.length()]=0;
	  };
	}

Then timing out. with the following displayed at the command line:

Server Ready. Listening on port: 69
Getting to GetInt
Getting to GetInt
Getting to GetInt
Getting to GetInt
Getting to GetInt

This is in the UdpData class, so the problem could be here, also this line

str.getBytes(0,str.length(),data,offset);

is showing in my code with a line through "getBytes" anychance this could be the cause.

Sorry Here is full code:

package tftps;
import java.net.*;
import java.io.*;
import java.util.*;
 
/**
 *
 * @author Error1
 */
public class TFTPS {
 
    /**
     * @param args the command line arguments
     */
 
        // TODO code application logic here
     public static final int tftpRRQ=1;
 	  public static final int tftpWRQ=2;
	  public static final int tftpDATA=3;
	  public static final int tftpACK=4;
	  public static final int tftpERROR=5;
 
	  public static final int maxTftpPakLen=516;
 
	  public static void main(String argv[]) {
              int port = 69;
	    try {
	      DatagramSocket sock = new DatagramSocket(port);
	      System.out.println("Server Ready.  Listening on port:  "+sock.getLocalPort());
 
	      for(;;) {
	        UdpData reqData = new UdpData(maxTftpPakLen);
	        DatagramPacket reqPak = reqData.mkPacket();
 
	        sock.receive(reqPak);
 
	        if (reqData.getInt(0)==tftpRRQ) {
	          System.out.println("Request from "+reqPak.getAddress());
 
	          tftpTransfer t = new tftpTransfer(reqPak);
	        }
	      }
	    }
	    catch(Exception e) { System.out.println("Server terminated"); }
	  }
	}

package tftps;
import java.net.*;
import java.io.*;
import java.util.*;
 
/**
 *
 * @author Error1
 */
class UdpData {
 
private byte data[];
 
 	  public UdpData(int len) { data = new byte[len]; };
 		  public UdpData(DatagramPacket pack) { data = pack.getData(); }
 
	  public byte[] getData() { return data; };
 
	  public int length() { return data.length; };
 
	  public DatagramPacket mkPacket() { return new DatagramPacket(data,data.length); };
 
	  public DatagramPacket mkPacket(int len) { return new DatagramPacket(data,len); };
 
	  public DatagramPacket mkPacket(InetAddress dest, int port) {
	    return new DatagramPacket(data,data.length,dest,port);
	  };
 
	  public DatagramPacket mkPacket(InetAddress dest, int port, int len) {
	    return new DatagramPacket(data,len,dest,port);
	  };
 
	  public int getInt(int offset) {
	System.out.println("Getting to GetInt");
	    // Fix to avoid sign extension
 
	    // Remember what the MSB is and then turn it off to avoid sign extension.  It is
	    // then added back to the sum after everything has been converted to integers.
 
	    byte lo = data[offset+1];
	    int signBit = (int)(lo&0x80);
	    lo&=0x7f;
 
	    // Standard TCP/IP byte order is hiByte followed by loByte (big endian)
 
	    int hiByte = (int)data[offset];
	    int loByte = (int)lo;
 
	    return (hiByte<<8)+signBit+loByte;
	  };
 
	  public void putInt(int val, int offset) {
	    int loByte = val%256;
	    int hiByte = val>>>8;
 
	    // Standard TCP/IP byte order is hiByte followed by loByte (big endian)
 
	    data[offset] = (byte)hiByte;
	    data[offset+1] = (byte)loByte;
	  };
 
	  public String getString(int offset) {
	    StringBuffer strBuf = new StringBuffer();
	    int curPos = offset;
 
	    while (data[curPos]!=0) {
	      strBuf.append((char)data[curPos]);
	      curPos++;
	    }
 
	    return new String(strBuf);
	  };
 
	  public void putString(String str, int offset) {
	    str.getBytes(0,str.length(),data,offset);
	    data[offset+str.length()]=0;
	  };
	}

package tftps;
import java.net.*;
import java.io.*;
import java.util.*;
 
/**
 *
 * @author Error1
 */
class tftpTransfer {
 
protected DatagramSocket sock;
     protected InetAddress clientIP;
    protected int clientPort;
    protected FileInputStream source;
    protected UdpData dataPak;
 
    public tftpTransfer(DatagramPacket reqPak) {
        System.out.println("Getting to reqPak");
      try {
        sock = new DatagramSocket();
 
        clientIP = reqPak.getAddress();
       clientPort = reqPak.getPort();
 
        UdpData reqData = new UdpData(reqPak);
 
        File srcFile = new File(reqData.getString(2));
 
        if (srcFile.exists() && srcFile.isFile() && srcFile.canRead()) {
          source = new FileInputStream(srcFile);
          dataPak = new UdpData(516);                             // 516==max pak len
          dataPak.putInt(3,0);                                    // 3==DATA opcode
 
 
        }
      } catch (Exception e) { System.out.println("Client failed"); };
    }
 
    public void run() {
        System.out.println("Getting run");
      int bytesRead = 512;
      DatagramPacket ack = new DatagramPacket(new byte[4],4);
 
      try {
        for (int blkNum=0; bytesRead==512; blkNum++) {            // 512==max data len
          dataPak.putInt(blkNum,2);
          bytesRead = source.read(dataPak.getData(),4,512);
          sock.send(dataPak.mkPacket(clientIP,clientPort,516));   // 516==max data len + header
 
          sock.receive(ack);
        }
      } catch (Exception e) { System.out.println("Client failed"); }
 
      try {
        source.close();
        sock.close();
      } catch (Exception e) {};
    }
}

No the print out is just a println I placed there as a debug. This shows that the server gets the clients request but it goes no further.

Its just a stand alone server so I have been using Tftpd32 App TFTPD32 : an opensource IPv6 ready TFTP server/service for windows : TFTP server , to connect to the server this running on a Virtual Machine, I have also tested it using a Cisco router to back up the routers configuration files none of which worked. Though I keep getting access denied error when I try to do this on my all on the same PC, i.e. client and server.

As well as command line prompt.

I have to go to work now, so any more advice would be mostly appreciated and I will reply to any questions later.

Found this client code if it helps:

package tftpclient;
import java.net.*;
import java.io.*;
import java.util.*;
 
/**
 *
 * @author Error1
 */
public class TftpClient {
 
    public static void main(String argv[]) {
       String host="",fileName="",line;
       int replyLen,blockNum = 0;
 
      try {
 
        // Process command line args.....
 
        InetAddress server = InetAddress.getByName(host);
       DatagramSocket sock = new DatagramSocket();
 
        FileOutputStream outFile = new FileOutputStream(fileName);
 
        // Create the request packet and send it off
 
        UdpData reqData = new UdpData(4+fileName.length()+5);     // 5==len("octet")
        reqData.putInt(1,0);                                      // RREQ opcode
        reqData.putString(fileName,2);                            // Requested file
        reqData.putString("octet",2+fileName.length()+1);         // Trans mode
 
        DatagramPacket pack = reqData.mkPacket(server,69);        // 69==TFTP port
        sock.send(pack);
 
        // Create the ACK packet
 
        UdpData ackData = new UdpData(4);
        ackData.putInt(4,0);                                      // ACK opcode
        DatagramPacket ackPack = ackData.mkPacket(server,69);
 
        // Create a packet to receive the data
 
        UdpData recData = new UdpData(516);                       // 516==max pak len
        pack = recData.mkPacket();
 
        for(int pakLen=516; pakLen==516; ) {
          sock.receive(pack);
 
          pakLen=pack.getLength();
 
          if (recData.getInt(0)==3) {                             // If a DATA pak then...            blockNum=recData.getInt(2);
 
            outFile.write(recData.getData(),4,pakLen-4);
 
            ackData.putInt(blockNum,2);
           ackPack = ackData.mkPacket(server,pack.getPort());
            sock.send(ackPack);
          }
          else
            throw new Exception();
        };
 
        outFile.close();
        sock.close();
      }
 
      catch (Exception e) { System.out.println("tftp session failed"); }
    }
  }

package tftpclient;
 
import java.net.*;
import java.io.*;
import java.util.*;
 
/**
 *
 * @author Error1
 */
class UdpData {
 
private byte data[];
 
 	  public UdpData(int len) { data = new byte[len]; };
 		  public UdpData(DatagramPacket pack) { data = pack.getData(); }
 
	  public byte[] getData() { return data; };
 
	  public int length() { return data.length; };
 
	  public DatagramPacket mkPacket() { return new DatagramPacket(data,data.length); };
 
	  public DatagramPacket mkPacket(int len) { return new DatagramPacket(data,len); };
 
	  public DatagramPacket mkPacket(InetAddress dest, int port) {
	    return new DatagramPacket(data,data.length,dest,port);
	  };
 
	  public DatagramPacket mkPacket(InetAddress dest, int port, int len) {
	    return new DatagramPacket(data,len,dest,port);
	  };
 
	  public int getInt(int offset) {
	System.out.println("Getting to getInt ");
	    // Fix to avoid sign extension
 
	    // Remember what the MSB is and then turn it off to avoid sign extension.  It is
	    // then added back to the sum after everything has been converted to integers.
 
	    byte lo = data[offset+1];
	    int signBit = (int)(lo&0x80);
	    lo&=0x7f;
 
	    // Standard TCP/IP byte order is hiByte followed by loByte (big endian)
 
	    int hiByte = (int)data[offset];
	    int loByte = (int)lo;
 
	    return (hiByte<<8)+signBit+loByte;
	  };
 
	  public void putInt(int val, int offset) {
	    int loByte = val%256;
	    int hiByte = val>>>8;
 
	    // Standard TCP/IP byte order is hiByte followed by loByte (big endian)
 
	    data[offset] = (byte)hiByte;
	    data[offset+1] = (byte)loByte;
	  };
 
	  public String getString(int offset) {
	    StringBuffer strBuf = new StringBuffer();
	    int curPos = offset;
 
	    while (data[curPos]!=0) {
	      strBuf.append((char)data[curPos]);
	      curPos++;
	    }
 
	    return new String(strBuf);
	  };
 
	  public void putString(String str, int offset) {
	    str.getBytes(0,str.length(),data,offset);
	    data[offset+str.length()]=0;
	  };
	}

Which when used displays:

Server Ready. Listening on port: 69
Getting to
Getting to
Getting to
Getting to
Getting to
Getting to
Request from /30.0.0.2
Getting to reqPak
Getting to sourcefile

At the command prompt. It will not do this with any other client.

Sorry for the delay in answering your questions, it seems to partially work when connecting to the server using a client (code above) that came as part of this server template. But it still will not work using a standard TFTP client i.e. command line etc. I understand its hard to test without some form of network. I have a network at home for my Cisco studies so I am able to do this.

I need this server to work with the TFTP clients that are coded into routers and switches opperating systems, also with the Windows 7 built in TFTP client that runs from the command line. I just can't understand why it will not transfer data even though its looping through the code. I have specified file to transfer on the client to the server, the server responds to connection but I am still getting a time out on the client and no file is transferred. Its all good fun but!

Yes I think I will be spending a few more late nights trying to solve this. But I will add some additional printlns and see what it shows.