extract coap query

Question

I need your help in extracting the query value in a coap message.The coap message looks like

coap://[ff08:90:5001:0:0:0:0:1]:12345/c?a=4

decoded packet is 52 02 00 00 91 63 63 61 3d 34 . Here 63 61 3d 34 is the query part ?a=4 . There is a data after query. I have pointed my buffer pointer to 63(?), now I'm struck in getting the value 34(4). How do I go to the value and extract it?

coap_h *hdr = (coap_h *)(buf);

buf = (uint8_t *)(hdr + 1);
len = buf[0] & 0xf;
buf += len + 1;

buf points to 52 initially and then I move the buf to the options field 91 and check for length then increment the buf which points to 63 (?). hope i'm clear this time.

can you show us the code please ? – iabdalkader Nov 07 '12 at 08:10 — iabdalkader, Nov 07 '12 at 08:10

score 2 · Answer 1 · edited Nov 25 '12 at 17:50

2

I don't have the time at the moment to parse your packet by hand, but you should know that the way options work has changed dramatically in CoAP-12. I have implemented some functions to encode and parse options, which you might find useful:

https://github.com/darconeous/smcp/blob/master/src/smcp/coap.c

https://github.com/darconeous/smcp/blob/master/src/smcp/coap.h

edited Nov 25 '12 at 17:50

andrewsi

10,807
132
35
51

answered Nov 25 '12 at 17:31

Robert Quattlebaum

388
2
10

extract coap query

1 Answers1