This example features a simple application listening for udp packets on port
0xF0B0 (src F0B1). It must be used in conjonction with a node running 
udp-sender-ipv6 example.

We use this example to test UDP, and most particularly UDP header compression
with IPv6 and 6lowpan support. When IPv6 is used over an 802.15.4 link, 
6lowpan acts as teh adaptation layer between IPv6 and MAC. In particular, it
can compress packet headers. IP header is compressed, as well as UDP header.

With both HC1 and HC01 header compression schemes, UDP 16-bit ports are 
compressed to 4 bits if they are between F0B0 and F0BF.

sender behavior:
The sender is implemented in apps/udp/udp-sender.c and acts the following way:
it waits 15 seconds (to be sure the node configures a global address, in case
a router on the link sends router advertisements usable for address 
autoconfiguration) , then sends 5 UDP packets to the receiver address 
entered staticvally in apps/udp/udp-sender.c.

receiver behavior:
When receiving a packet, the receiver answers with a simmilar packet.

To run this example, contiki-conf.h must have at least the following flags 
values:
#define UIP_CONF_UDP             1
#define UIP_CONF_IPV6            1

You must configure addresses in apps/udp/udp-sender.c and apps/udp/udp-receiver.c
which match your platforms addresses.



