A Quick Introduction to the Erbium (Er) REST Engine

EXAMPLE FILES

• er-example-server.c: A RESTful server example showing how to use the REST layer to develop server-side applications (at the moment only CoAP is implemented for the REST Engine).
• er-example-client.c: A CoAP client that polls the /actuators/toggle resource every 10 seconds and cycles through 4 resources on button press (target address is hard-coded).
• er-plugtest-server.c: The server used for draft compliance testing at ETSI IoT CoAP Plugtests. Erbium (Er) participated in Paris, France, March 2012 and Sophia-Antipolis, France, November 2012 (configured for minimal-net).

PRELIMINARIES

• Make sure rpl-border-router has the same stack and fits into mote memory: You can disable RDC in border-router project-conf.h (not really required as BR keeps radio turned on). #undef NETSTACK_CONF_RDC #define NETSTACK_CONF_RDC nullrdc_driver
• For convenience, define the Cooja addresses in /etc/hosts aaaa::0212:7401:0001:0101 cooja1 aaaa::0212:7402:0002:0202 cooja2 ...
• Get the Copper (Cu) CoAP user-agent from https://addons.mozilla.org/en-US/firefox/addon/copper-270430
• Optional: Save your target as default target make TARGET=sky savetarget

COOJA HOWTO

###Server only:

make TARGET=cooja server-only.csc

Open new terminal

make connect-router-cooja

• Start Copper and discover resources at coap://cooja2:5683/
• Choose "Click button on Sky 2" from the context menu of mote 2 (server) after requesting /test/separate
• Do the same when observing /test/event

###With client:

make TARGET=cooja server-client.csc

Open new terminal

make connect-router-cooja

• Wait until red LED toggles on mote 2 (server)
• Choose "Click button on Sky 3" from the context menu of mote 3 (client) and watch serial output

TMOTES HOWTO

###Server:

1. Connect two Tmote Skys (check with $ make TARGET=sky sky-motelist)

    make TARGET=sky er-example-server.upload MOTE=2
    make TARGET=sky login MOTE=2
   

2. Press reset button, get address, abort with Ctrl+C: Line: "Tentative link-local IPv6 address fe80:0000:0000:0000::::"

    cd ../ipv6/rpl-border-router/
    make TARGET=sky border-router.upload MOTE=1
    make connect-router
   

   For a BR tty other than USB0:

    make connect-router-port PORT=X
   

3. Start Copper and discover resources at:

    coap://[aaaa::____:____:____:____]:5683/
   

Add a client:

1. Change the hard-coded server address in er-example-client.c to aaaa:::::

2. Connect a third Tmote Sky

    make TARGET=sky er-example-client.upload MOTE=3
   

MINIMAL-NET HOWTO

With the target minimal-net you can test your CoAP applications without constraints, i.e., with large buffers, debug output, memory protection, etc. The er-plugtest-server is thought for the minimal-net platform, as it requires an 1280-byte IP buffer and 1024-byte blocks.

    make TARGET=minimal-net er-plugtest-server
    sudo ./er-plugtest-server.minimal-net

Open new terminal

    make connect-minimal

• Start Copper and discover resources at coap://[fdfd::ff:fe00:10]:5683/
• You can enable the ETSI Plugtest menu in Copper's preferences

Under Windows/Cygwin, WPCAP might need a patch in \usr\include\w32api\in6addr.h:

21,23c21
< #ifdef __INSIDE_CYGWIN__
<     uint32_t __s6_addr32[4];
< #endif
---
>     u_int __s6_addr32[4];
36d33
< #ifdef __INSIDE_CYGWIN__
39d35
< #endif

DETAILS

Erbium currently implements draft 13. Central features are commented in er-example-server.c. In general, apps/er-coap-13 supports:

• All draft 13 header options
• CON Retransmissions (note COAP_MAX_OPEN_TRANSACTIONS)
• Blockwise Transfers (note REST_MAX_CHUNK_SIZE, see er-plugtest-server.c for Block1 uploads)
• Separate Responses (no rest_set_pre_handler() required anymore, note coap_separate_accept(), _reject(), and _resume())
• Resource Discovery
• Observing Resources (see EVENT_ and PRERIODIC_RESOURCE, note COAP_MAX_OBSERVERS)

REST IMPLEMENTATIONS

The Makefile uses WITH_COAP to configure different implementations for the Erbium (Er) REST Engine.

• WITH_COAP=13 uses Erbium CoAP 13 apps/er-coap-13/. The default port for coap-13 is 5683.
• WITH_COAP=12 uses Erbium CoAP 12 apps/er-coap-12/. The default port for coap-12 is 5683.
• WITH_COAP=7 uses Erbium CoAP 08 apps/er-coap-07/. The default port for coap-07/-08 is 5683.
• WITH_COAP=3 uses Erbium CoAP 03 apps/er-coap-03/. The default port for coap-03 is 61616. er-coap-03 produces some warnings, as it not fully maintained anymore.
• WITH_COAP=0 is a stub to link an Erbium HTTP engine that uses the same resource abstraction (REST.x() functions and RESOURCE macros.

TODOs

• Dedicated Observe buffers
• Optimize message struct variable access (directly access struct without copying)
• Observe client
• Multiple If-Match ETags
• (Message deduplication)