7 replies to this topic

[nsx]

I get an "Access violation" error when I try to download files from Tftpd32 or Tftpd64 running on a Windows Server 2008 R2. The TFTP client is atftp on a computer running Debian Linux. The same atftp command is able to download files from Tftpd32 running on a Windows XP computer on the same network. Does any one here know the cause of this error? A Google search on the topic does not turn up much useful information. Thanks.

[Sha0]

Is the error observed on the client Linux system or the server Windows system?

[nsx]

the error is observed on the Linux client and in Wireshark. the Tftpd log file on the Windows server does not get any entries in it

[Sha0]

Is there a firewall interfering with TFTPD32 or TFTPD64 on the Windows server? If you perform a Wireshark capture on the Windows server, do you see the incoming TFTP requests?

[nsx]

The Windows firewall has been turned off. In Wireshark on the server I see the incoming TFTP request. It is followed by the "Access violation" error. Decoding the payload of the UDP packet gives this"

 

Trivial File Transfer Protocol

Source File: vxWorks

Opcode: Error Code (5)

Error code: Illegal TFTP Operation (4)

Error message: Access violation.

[Sha0]

In Wireshark on the server I see the incoming TFTP request. It is followed by the "Access violation" error. Decoding the payload of the UDP packet gives this"
 
Trivial File Transfer Protocol
Source File: vxWorks
Opcode: Error Code (5)
Error code: Illegal TFTP Operation (4)
Error message: Access violation.

I'd suggest looking at the source and destination IP addresses and the source and destination MAC addresses. Is the server's IP address involved in the TFTP packets?

[nsx]

the source and destination MAC and IP addresses in the captured packets do match the addresses of the hosts where the client and server are installed.

[Sha0]

the source and destination MAC and IP addresses in the captured packets do match the addresses of the hosts where the client and server are installed.

That suggests that the response is indeed coming from the server. You can use TCPView.exe or

netstat -ao | findstr tftp

to find out if TFTPD32 (or 64) owns the TFTP port and actually the process responsible for this response.

If it is, then the error message it is giving is trying to tell you something. In that case, I'd suggest checking filesystem permissions and whether or not any other processes have the vxWorks file locked. Process Monitor (ProcMon.exe) might come in handy for that.