[mrtg] Re: MRTG losing Bytes in Octet string

[David Landgren]

Rene Buechler wrote:

> 
> 
> 
> Hi
> I'm using MRTG 2.10.13 on a Windows NT workstation.
> I'm scanning on our Ficon Directors FC/9000 (CNT) the Rx- and TxFrames to
> check the utilisation of each FC-Port.
> These Directors will give me back a 64-Bit counter value as an octet
> string.
> To convert this octet string I'm using the option ConversionCode and a
> small perl script.
> Now I have seen, that some values from the counters are wrong. I've found,
> that when inside an octet string is a Hex Byte with 0x0a or 0x0d these
> bytes gets lost. In this case, MRTG will handover to my subroutine only
> seven Bytes instead of 8 Bytes. I made a lot of tests and testet each hex
> code from 00 ... FF. Every hex code is ok except the two ones with Hex
> codes 0x0a and 0x0d which gets lost.

Hmm, I smell newline munging. Unix represents newlines with the single 
character \x0d but DOS (Windows) uses \x0d\x0a. This is why (among other 
reasons) we have ASCII and Binary transfers in FTP: it lets the programs 
munge the newlines correctly so that text files get displayed correctly. 
Of course, when you are dealing with binary data you don't want that to 
happen. I suspect this is what is happening to you.

In your Perl script, make sure you do a binmode on your output handle, 
before it prints anything, e.g.:

binmode STDOUT;
print $counter;

David

> Had someone allready this problem?
> 
> Regards Rene Buechler
> 
> 
> 
> 
> 
> 
> 
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