task-06

previous task

6. UDP Client / Server

The transport layer (UDP, TCP, etc) is accessed through conn driver API

Look at the new modules in the Makefile

USEMODULE += gnrc_conn_udp

udp.c utilizes conn_udp_sendto() and conn_udp_recvfrom() to exchange UDP packets

Task 6.1: Use UDP for messaging

1. Compile and run on two native instances
2. We have two new shell commands: udps to start a server and udp to send a message.

> help
help
Command              Description
---------------------------------------
udp                  send udp packets
udps                 start udp server
reboot               Reboot the node
ps                   Prints information about running threads.
ping6                Ping via ICMPv6
random_init          initializes the PRNG
random_get           returns 32 bit of pseudo randomness
ifconfig             Configure network interfaces
ncache               manage neighbor cache by hand
routers              IPv6 default router list
>

3. Start a UDP server on port 8888 with udps 8888. Look at the output of ps

> ps
ps
      pid | name                 | state    Q | pri | stack ( used) | location
        1 | idle                 | pending  Q |  15 |  8192 ( 6240) | 0x806eb80
        2 | main                 | running  Q |   7 | 12288 ( 9312) | 0x806bb80
        3 | ipv6                 | bl rx    _ |   4 |  8192 ( 6240) | 0x807bce0
        4 | udp                  | bl rx    _ |   5 |  8192 ( 6240) | 0x807f760
        5 | gnrc_netdev2_tap     | bl rx    _ |   4 |  8192 ( 6240) | 0x8079ca0
        6 | UDP Server           | bl rx    _ |   6 |  8192 ( 6240) | 0x8077c60
          | SUM                  |            |     | 53248 (40512)
>

The new thread for the UDP server has the PID 6 in this example.

4. Get your IPv6 address using ifconfig

   > ifconfig
   ifconfig
   Iface  5   HWaddr: 22:7e:b9:04:9f:f0
   
              MTU:1500  HL:64
              Source address length: 6
              Link type: wired
              inet6 addr: ff02::1/128  scope: local [multicast]
              inet6 addr: fe80::207e:b9ff:fe04:9ff0/64  scope: local
              inet6 addr: ff02::1:ff04:9ff0/128  scope: local [multicast]
   

5. From the second instance, send a udp packet with the udp command.

   > udp fe80::207e:b9ff:fe04:9fef 8888 hello
   udp fe80::207e:b9ff:fe04:9fef 8888 hello
   Success: send 5 byte to fe80::207e:b9ff:fe04:9fef
   

Task 6.2: Communicate with Linux

1. Compile and run on two native instances

2. Start a UDP server on port 8888 with udps 8888.

3. Send a packet to RIOT from Linux using netcat

   echo "hello" | nc -6u <RIOT-IPv6-addr>%tapbr0 8888

   Note: on MAC use bridge0 instead of tapbr0.

4. Start a UDP server on the host machine with netcat.

   nc -6lu 8888
   

   And in RIOT ...

   udp <tap0-IPv6-addr> 8888 hello
   

Read the Doc

Task 6.3 -- Exchange UDP packets with your neighbors

• Compile, flash and run on the board BOARD=samr21-xpro make all flash term
• Send and receive UDP messages to and from your neighbors using udp and udps

next task