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examples/gnrc_networking: add explanation for RIOT<->RIOT communication
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Lotte Steenbrink
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# gnrc_networking example
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This example shows you how to try out the code in two different ways: Either by communicating
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between the RIOT machine and its Linux host, or by communicating between two RIOT instances.
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Note that the former only works with native, i.e. if you run RIOT on your Linux machine.
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## Connecting RIOT native and the Linux host
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> **Note:** RIOT does not support IPv4, so you need to stick to IPv6 anytime. To establish a connection between RIOT and the Linux host,
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you will need `netcat` (with IPv6 support). Ubuntu 14.04 comes with netcat IPv6 support pre-installed. On Debian it's available in the
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package `netcat-openbsd`. Be aware that many programs require you to add an option such as -6 to tell them to use IPv6, otherwise they
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will fail. If you're using a _Raspberry Pi_, run `sudo modprobe ipv6` before trying this example, because raspbian does not load the
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IPv6 module automatically.
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On some systems (openSUSE for example), the _firewall_ may interfere, and prevent some packets to arrive at the application (they will
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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).
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> **Note:** RIOT does not support IPv4, so you need to stick to IPv6 anytime. To
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establish a connection between RIOT and the Linux host, you will need `netcat`
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(with IPv6 support). Ubuntu 14.04 comes with netcat IPv6 support pre-installed.
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On Debian it's available in the package `netcat-openbsd`. Be aware that many
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programs require you to add an option such as -6 to tell them to use IPv6, otherwise they
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will fail. If you're using a _Raspberry Pi_, run `sudo modprobe ipv6` before trying
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this example, because raspbian does not load the IPv6 module automatically.
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On some systems (openSUSE for example), the _firewall_ may interfere, and prevent
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some packets to arrive at the application (they will however show up in Wireshark,
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which can be confusing). So be sure to adjust your firewall rules, or turn it off
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(who needs security anyway).
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First, create a tap interface:
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sudo ip tuntap add tap0 mode tap user ${USER}
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sudo ip link set tap0 up
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Now you can start the `gnrc_networking` example by invoking `make term`. This should automatically connect to the `tap0` interface. If
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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_networking` directory):
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Now you can start the `gnrc_networking` example by invoking `make term`. This should
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automatically connect to the `tap0` interface. If this doesn't work for any reason,
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run make term with the tap0 interface as the PORT environment variable:
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PORT=tap0 make term
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To verify that there is connectivity between RIOT and Linux, go to the RIOT console and run `ifconfig`:
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@ -26,13 +37,17 @@ To verify that there is connectivity between RIOT and Linux, go to the RIOT cons
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inet6 addr: fe80::ccf5:e1ff:fec5:f75a/64 scope: local
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inet6 addr: ff02::1:ffc5:f75a/128 scope: local [multicast]
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Copy the [link-local address](https://en.wikipedia.org/wiki/Link-local_address) of the RIOT node (prefixed with `fe80`) and try to ping it **from the Linux node**:
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Copy the [link-local address](https://en.wikipedia.org/wiki/Link-local_address)
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of the RIOT node (prefixed with `fe80`) and try to ping it **from the Linux node**:
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ping6 fe80::ccf5:e1ff:fec5:f75a%tap0
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Note that the interface on which to send the ping needs to be appended to the IPv6 address, `%tap0` in the above example. When talking to the RIOT node, you always want to send to/receive from the `tap0` interface.
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Note that the interface on which to send the ping needs to be appended to the IPv6
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address, `%tap0` in the above example. When talking to the RIOT node, you always want
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to send to/receive from the `tap0` interface.
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If the pings succeed you can go on to send UDP packets. To do that, first start a UDP server on the RIOT node:
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If the pings succeed you can go on to send UDP packets. To do that, first start a
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UDP server on the RIOT node:
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> udp server start 8808
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Success: started UDP server on port 8808
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@ -41,9 +56,12 @@ Now, on the Linux host, you can run netcat to connect with RIOT's UDP server:
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nc -6uv fe80::ccf5:e1ff:fec5:f75a%tap0 8808
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The `-6` option is necessary to tell netcat to use IPv6 only, the `-u` option tells it to use UDP only, and the `-v` option makes it give more verbose output (this one is optional).
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The `-6` option is necessary to tell netcat to use IPv6 only, the `-u` option tells
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it to use UDP only, and the `-v` option makes it give more verbose output (this one is optional).
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You should now see that UDP messages are received on the RIOT side. Opening a UDP server on the Linux side is also possible. To do that, write down the IP address of the host (run on Linux):
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You should now see that UDP messages are received on the RIOT side. Opening a UDP
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server on the Linux side is also possible. To do that, write down the IP address
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of the host (run on Linux):
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ifconfig tap0
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tap0 Link encap:Ethernet HWaddr ce:f5:e1:c5:f7:59
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@ -62,4 +80,63 @@ Now, on the RIOT side, send a UDP packet using:
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udp send fe80::4049:5fff:fe17:b3ae 8808 testmessage
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You should see `testmessage` appear in netcat. Instead of using netcat, you can of course write your own software, but you may have to bind the socket to a specific interface (tap0 in this case). For an example that shows how to do so, see [here](https://gist.github.com/backenklee/dad5e80b764b3b3d0d3e).
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You should see `testmessage` appear in netcat. Instead of using netcat, you can of
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course write your own software, but you may have to bind the socket to a specific
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interface (tap0 in this case). For an example that shows how to do so, see
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[here](https://gist.github.com/backenklee/dad5e80b764b3b3d0d3e).
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## Connecting two RIOT instances
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When using native (i.e. when you're trying this on your Linux machine), you first
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need to set up two tap devices and a bridge that connects them. This constitutes a
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virtual network that the RIOT instances can use to communicate.
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./../../dist/tools/tapsetup/tapsetup --create 2
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Then, make sure you've compiled the application by calling `make` and start the
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first RIOT instance by invoking `make term`. In the RIOT shell, get to know the
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IP address of this node:
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> ifconfig
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Iface 7 HWaddr: ce:f5:e1:c5:f7:5a
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inet6 addr: ff02::1/128 scope: local [multicast]
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inet6 addr: fe80::ccf5:e1ff:fec5:f75a/64 scope: local
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inet6 addr: ff02::1:ffc5:f75a/128 scope: local [multicast]
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and start a UDP server.
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> udp server start 8808
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This node is now ready to receive data on port `8808`.
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In a second terminal, start a second RIOT instance, this time listening on `tap1`:
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PORT=tap1 make term
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In the RIOT shell, you can now send a message to the first RIOT instance:
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> udp send fe80::ccf5:e1ff:fec5:f75 8808 testmessage
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*(Make sure to copy the actual
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[link-local address](https://en.wikipedia.org/wiki/Link-local_address) of your first
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RIOT instance into the above command)*
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In your first terminal, you should now see output that looks like this.
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> PKTDUMP: data received:
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~~ SNIP 0 - size: 11 byte, type: NETTYPE_UNDEF (0)
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000000 74 65 73 74 6d 65 73 73 61 67 65
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~~ SNIP 1 - size: 8 byte, type: NETTYPE_UDP (3)
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src-port: 8808 dst-port: 8808
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length: 19 cksum: 0x4d95f
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~~ SNIP 2 - size: 40 byte, type: NETTYPE_IPV6 (1)
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traffic class: 0x00 (ECN: 0x0, DSCP: 0x00)
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flow label: 0x00000
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length: 19 next header: 17 hop limit: 64
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source address: fe80::a08a:84ff:fe68:544f
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destination address: fe80::60fc:3cff:fe5e:40df
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~~ SNIP 3 - size: 20 byte, type: NETTYPE_NETIF (-1)
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if_pid: 6 rssi: 0 lqi: 0
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src_l2addr: a2:8a:84:68:54:4f
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dst_l2addr: 62:fc:3c:5e:40:df
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~~ PKT - 4 snips, total size: 79 byte
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