Test application: picoserver_uboot

The picoserver_uboot test application has only been built using the camkes framework.

Overview of the picoserver_uboot test application

It is not the purpose of this developer kit to give a CAmkES tutorial (e.g. see seL4's documentation), but this application is based on the following CAmkES model:

Picoserver CAmkES overview

EthDriverUboot is a simple implementation of an Ethernet driver that has been ported from U-Boot. PicoServer provides a picoTCP TCP/IP stack on top of this, and the Echo component simply listens on port 1234 of a given IP address, echoing received characters on the display. (An additional component TimeServer has been omitted from the diagram for clarity, but see the case study application for more details.)

Instructions for running picoserver_uboot

As usual, this assumes that the user is already running a the CAmkES docker container within the build environment, where we can create a directory and clone the code and dependencies.

mkdir /host/uboot_pico
cd /host/uboot_pico

repo init -u https://github.com/sel4devkit/camkes-manifest.git

repo sync

From the /host/uboot_pico directory, execute the following commands:

mkdir build
cd build

../init-build.sh -DCAMKES_APP=picoserver_uboot -DPLATFORM=maaxboard -DSIMULATION=FALSE -DPICOSERVER_IP_ADDR=xxx.xxx.xxx.xxx
ninja

where xxx.xxx.xxx.xxx is the IP address to allocate to the MaaXBoard.

A successful build will result in an executable file called capdl-loader-image-arm-maaxboard in the images subdirectory.

When the picoserver_uboot application is running on the MaaXBoard, it should confirm that it is listening on port 1234 of the supplied IP address. It will also confirm registration of the protocol stack layers. The application allocates a random MAC address.

At any time while running, the application may display No such port .... messages as it monitors traffic on the network; this is expected behaviour that may be ignored.

Meanwhile, from a terminal window on the host machine, use the netcat (nc) command (native to Linux or macOS, or available as a download for Windows), where xxx.xxx.xxx.xxx is the IP address of the MaaXBoard, as previously specified:

nc xxx.xxx.xxx.xxx 1234

On the MaaXBoard (via CoolTerm as usual), a message like the following should be seen:

echo: Connection established with yyy.yyy.yyy.yyy on socket 1

where yyy.yyy.yyy.yyy is the IP address of the host machine.

From the host machine's terminal, strings may be typed until nc is terminated with Ctrl-C:

hostmachine ~ % nc 192.168.0.111 1234
Hello world!
Goodbye
^C
hostmachine ~ %

Each time carriage return is entered, the picoserver_uboot application will display the string, until the nc session is terminated, upon which the connection will be closed:

echo: Connection established with 192.168.0.11 on socket 1
echo: Received message of length 13 --> Hello world!
echo: Received message of length 8 --> Goodbye
echo: Connection closing on socket 2
echo: Connection closed on socket 2

Connections can be re-established simply by issuing another nc command.

Implementation note

Connecting, disconnecting, and reconnecting to a network can give rise to delays in the order of a few minutes while the elements in the network handshake and resynchronise, particularly in the case of our application, which assigns a random MAC address to the same IP address each time it runs. If the connection is not established promptly, the easiest remedial options are:

  • Start from a clean reboot of the host machine (which will include flushing its DNS cache); or
  • Be patient! (If you are prepared to wait for a few minutes, the connection will be made. Note that nc may timeout after a while if no connection is made, so the command would need to be repeated.)