[ns] Help: accessing contents of data payload in NS2

[O S]

Hi,

I am trying to access the contents of the data payload of a packet in NS2
i.e. the actual bits of data. I have something like this:

from packet.h, I can see that it has functions 'accessdata' and 'userdata'
both of which return the data payload one way or another. But when I do
this:


if((PacketData*)p->userdata()!=NULL) {
        PacketData* packdata = (PacketData*)p->userdata();
        char* pdata = (char*)packdata->data();
        printf("data = %c\n", pdata);
        }

if (p->accessdata()!=NULL){
        data_char = p->accessdata();
        printf("data = %c and p->datalength = %d real length = %d \n",
data_char, p->datalen(), ((PacketData*)(p->userdata()))->size() );
        }

I get the correct lengths of the packet, but data is empty...prints just
empty space.

Can anyone help me access the contents of the data payload in NS2? I need to
compare the contents of two packets. Any other ideas.

Thanks

PS: in one documentation for NS2, I read something which seems to suggest
that the payload of packets in NS2 does not contain anything because its
only a simulated packet. Any ideas?