I want code capable of listening for network input (possibly a connect() on an unexpected port) and reading the raw packet, going as low as the IP layer. I don't want to write the code that does all that, so I decided to use Net::Packet::Dump. I started with the first half of the example in the POD of Net::Packet::Dump:

   # Instanciate object, will start capturing from network
   my $dump = Net::Packet::Dump->new(
      filter  => 'tcp',
      noStore => 1,
   );

   while (1) {
      if (my $frame = $dump->next) {
         do_stuff($frame);
      }
   }
[download]

I get an error: Can't bless non-reference value at .../Dump.pm line 250. So I tried perl -d server.pl. The error occurs at this expression:

bless(Net::Packet::netpacket_pcap_fp($self->_pcapd), 'IO::File')
[download]

Net::Packet::netpacket_pcap_fp is a reference to a C function:

FILE * netpacket_pcap_fp(pcap_t *pd){
   if (pd == NULL) return(0);
   else return(pd->sf.rfile);
}
[download]

and when I print $self->_pcapd in the debugger, I get

'_pcapd' => pcap_tPtr=SCALAR(0x896dde8)
   -> 144211632
[download]

which I think is a reference (pointer) to the beginning of the data structure written in C of type struct pcapd, which is defined as follows:

struct pcap_sf {
    FILE *rfile;
    ...
};
...
struct pcap {
    ...
    struct pcap_sf sf;
    ...
};
[download]

So it looks like Net::Packet::Dump is trying to get a FILE* from C and bless it as an 'IO::File'. I've tried many things, even downloading the PeepPoke module so I could inspect that C data structure to be sure that FILE*rfile is not null (and no, it is not null). I found no reference online that suggests others may be having this problem.

I am grateful for any advice you can give! Thanks in advance!

--jeffguy

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