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gnrc_tftp example

Connecting RIOT native and the Linux host

Note: RIOT does not support IPv4, so you need to stick to IPv6 anytime. To establish a connection between RIOT and the Linux host, you will need tftp (with IPv6 support). On Ubuntu and Debian you would need the package tftp-hpa for TFTP client and tftpd-hpa for TFTP server. Be aware that many programs require you to add an option such as -6 to tell them to use IPv6, otherwise they will fail. If you're using a Raspberry Pi, run sudo modprobe ipv6 before trying this example, because raspbian does not load the IPv6 module automatically. On some systems (openSUSE for example), the firewall may interfere, and prevent some packets to arrive at the application (they will however show up in Wireshark, which can be confusing). So be sure to adjust your firewall rules, or turn it off (who needs security anyway).

First, create a tap interface (to which RIOT will connect) and a bridge (to which Linux will connect) from the RIOT main directory run:

./dist/tools/tapsetup/tapsetup -c 1

Now you can start the gnrc_tftp example by invoking make term. This should automatically connect to the tap0 interface. If this doesn't work for some reason, run make without any arguments, and then run the binary manually like so (assuming you are in the examples/gnrc_tftp directory):

To verify that there is connectivity between RIOT and Linux, go to the RIOT console and run ifconfig:

> ifconfig
Iface  6   HWaddr: 7e:ed:d2:ee:e1:07
       Source address length: 6
       Link type: wired
       inet6 addr: ff02::1/128  scope: local [multicast]
       inet6 addr: fe80::7ced:d2ff:feee:e107/64  scope: local
       inet6 addr: ff02::1:ffee:e107/128  scope: local [multicast]

Copy the link-local address of the RIOT node (prefixed with fe80) and try to ping it from the Linux node:

ping6 fe80::7ced:d2ff:feee:e107%tapbr0

Note that the interface on which to send the ping needs to be appended to the IPv6 address, %tapbr0 in the above example. When talking to the RIOT node, you always want to send to/receive from the tapbr0 interface.

If the pings succeed you can go on to send UDP packets. To do that, first start a UDP server on the RIOT node:

> tftps start
tftp_server: Starting TFTP service at port 69

Now, on the Linux host, you can run tftp to connect with RIOT's TFTP server:

$ tftp -v -6 fe80::7ced:d2ff:feee:e107%tapbr0 -c get welcome.txt

The output will be something like:

Connected to fe80::7ced:d2ff:feee:e107%tapbr0 (fe80::7ced:d2ff:feee:e107), port 69
getting from fe80::7ced:d2ff:feee:e107%tapbr0:welcome.txt to welcome.txt [netascii]
Received 94 bytes in 0.0 seconds [113425 bit/s]

The -6 option is necessary to tell tftp to use IPv6 only and the -v is to tell the tftp client to be verbose.

You should now see that the TFTP messages are received on the RIOT side. Opening a TFTP server on the Linux side is also possible. To do that, write down the IP address of the host (run on Linux):

ifconfig tapbr0
tapbr0    Link encap:Ethernet  HWaddr 0e:bc:0f:49:7f:e4
          inet6 addr: fe80::cbc:fff:fe49:7fe4/64 Scope:Link
          RX packets:22 errors:0 dropped:0 overruns:0 frame:0
          TX packets:53 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:1928 (1.9 KB)  TX bytes:6217 (6.2 KB)

And start the tftp server on Linux:

$ sudo /etc/init.d/tftpd-hpa stop && mkdir -p tftpserv && echo "hello world" > tftpserv/welcome.txt && sudo in.tftpd -vvv -L -6 -c -s -u ${USER} ./tftpserv

Now, on the RIOT side, send a UDP packet using:

tftpc get welcome.txt octet 1 fe80::cbc:fff:fe49:7fe4

You will get output that looks like this:

tftp_client: bin read welcome.txt:12

hello worl


tftp_client: SUCCESS: (null)