1. Using Prosody with a HTTP Reverse Proxy

    It's been a while since I first installed prosody on Agayon.be. I use it to experiments with my bots, to keep contact with the XMPP community and discover new cool stuffs to do. Recently I struggled a bit because I wanted to hide the prosody small HTTP server behind my Proxy. For various reasons, I still use Apache 2.4 and I could not get it to work with prosody. I mostly use the HTTP server for bosh authentication with Converse.js and with the http_upload module. When the 5281 port was accessible and Prosody handled the requests directly on the internet it worked well. But when I followed the documentation to use a proxy, it stopped working. All my PUT requests got a 404 error. I tested my setup with Slixmpp and the http_upload example.

    Here is my configuration before the fix:


    Main config

    https_ports = { 5281 }
    https_interfaces = {  "", "::1" }
    trusted_proxies = { "", "::1"}


    Component "upload.example.com" "http_upload"
           http_max_content_size = 10485760
           http_external_url = "https://upload.example.com/"

    Apache VirtualHost

    ProxyPass / http://localhost:5280/
    ProxyPassReverse / http://localhost:5280/



    DEBUG    SEND: <iq id="23efd54cf4b2487386852e800f2ea411" to="upload.example.com" type="get"><request xmlns="urn:xmpp:http:upload:0" filename="robot.png" size="118037" content-type="image/png" /></iq>
    DEBUG    RECV: <iq type="result" id="23efd54cf4b2487386852e800f2ea411" from="upload.example.com" to="test@example.com/test"><slot xmlns="urn:xmpp:http:upload:0"><get url="https://upload.example.com/upload/au5rOiUMomJbDI3q/robot.png" /><put url="https://upload.example.com/upload/au5rOiUMomJbDI3q/robot.png" /></slot></iq>
    ERROR    Could not upload file: 404 (<!DOCTYPE html>
    <meta charset="utf-8">
    <title>404 Not Found</title>


    Mar 21 10:02:42 c2s5586c8e88960 debug   Received[c2s]: <iq id='23efd54cf4b2487386852e800f2ea411' type='get' to='upload.example.com'>
    Mar 21 10:02:42 c2s5586c8e88960 debug   Given upload slot "au5rOiUMomJbDI3q/robot.png"
    Mar 21 10:02:42 c2s5586c8e88960 debug   Sending[c2s]: <iq type='result' id='23efd54cf4b2487386852e800f2ea411' from='upload.example.com' to='memo@agayon.be/test'>
    Mar 21 10:02:42 socket  debug   server.lua: accepted new client connection from ::1:49436 to 5280
    Mar 21 10:02:42 http.server debug   Firing event: PUT /upload/au5rOiUMomJbDI3q/robot.png
    Mar 21 10:02:42 http.server debug   Firing event: PUT localhost/upload/au5rOiUMomJbDI3q/robot.png

    What is important to see is the second event:

    PUT localhost/upload/au5rOiUMomJbDI3q/robot.png

    on a working configuration it is

    PUT upload.example.com/upload/au5rOiUMomJbDI3q/robot.png

    The fix

    After a small discussion with Link Mauve from JabberFr, he suggested me to use setup the proxy to tell him to force its headers:


        RequestHeader set Host "upload.example.com"
        ProxyPreserveHost On
        ProxyPass / http://localhost:5280/
        ProxyPassReverse / http://localhost:5280/


    proxy_set_header Host "upload.example.com";

    Two small lines and now it is working as expected :-).


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  2. What have I done ?


    During these weird time of corona virus crisis, like many, I am working from home and cancelled all social activities. Apart from the distanciation, the virus, the lack of activities, it has been a quite fruitful period as I work a lot on the robot. This articles sums up the latest developments and achievements.

    New functionnalities

    My robot, the Agayon has now kite a lot more features. Among which:

    • Video streaming nearly in real time. The stream can be viewed in a web browser. It works quite well and has been used across the internet. Some friends or family members have visited me with the help of the robot. The only drawback is that I have to limit the stream to 10 frames per second. The setup is based on mjpg-streamer and the custom layout is available on his dedicated Gitlab repository.
    • The Agayon can now be remotely controlled with
      • A PS4 controller (Bluetooth)
      • REST API to control the robot.
      • A web interface that uses the API (see screenshot below)
    • Lidar mapping: It can be triggered by the PS4 controller, the web interface or XMPP. I use a RPLidar A1M8. Data is saved in a file that can be analyzed afterward. No real time data processing for now.
    • XMPP: migration from the deprecated Sleekxmpp library to the more modern one Slixmpp.


    Python (Raspberry Pi)

    The code is available on my gitlab account.

    • Small turn angles for remote control. The robot was sometime too much brutal during rotation. This version adds the support for 'gentle turns'. During the new gentle turns, only one wheel is moving. The 'normal turn' remains and it rotates both wheels in opposite direction.
    • Start and Stop Webcam streaming from socket. It relies on the restart_stream.sh and stop_stream.sh scripts. It is used from the web interface and XMPP.
    • Mapping: simple scan and logging of all mapping data. It Saves a picture (polar graph) for each snapshot.
    • Arduino communication: serial data to get the ultrasonic sensors measurements.
    • The rover can be remotely controlled with a PS4 controller. Events are caught and instructions are sent through serial communication to Arduino.
    • Some refactoring and cleaning.
    • A lot of bug fix.


    The code is available on the gitlab repository.

    • I created a small Serial manager to handle orders from the RPI. It can be used to remotely control the motors, get ultrasonic measurements, change speed, change mode (incremental or directly to a mode number), capacity to turn a little (small angles but not that small )
    • Send formatted serial data that can be easily parsed by the RPI process (odometry).
    • A lot of bug fix


    The web remote control is based on a small webservice depending on with the Flask framework. It is served with uWSGI with the help of Nginx. The sources are on the Gitab related repository. It is used to control the robot with a web interface but any client able to use a web API can use it. Maybe an Android client will follow?

    When the video streaming service is unavailable, a 503 error is displayed with a custom page.

    503 error

    I use it to launch the Webcam streaming directly from the navigator.

    All the configuration, HTML pages, scripts and config files are available in a separate repository.

    Once mjpg_streamer is launched, it serves a small page to interact with the API.

    This picture was taken at the beginning of a ~4m narrow hallway.



    Here are some pictures token in my apartment. As long as no Lidar measurment has been made, a cartoonish picture of the robot is displayed. As the robot is going forward, the mapping is updated by clicking on the Lidar camera button. For unknown reason, the left/right mapping is inverted in the picture.


    Start Lidar Start Lidar


    Middle Lidar


    End Lidar


    There are still a lot of room for improvements. Here are some ideas to occupy me in the future:

    • Automatically save a camera picture when the lidar mapping is triggered.
    • Detect the kernel messages about battery. When the voltage is too low, the information is logged by the kernel and can be found with systemd. The idea would be to shut down the robot when necessary to avoid SD card memory corruption.
    • Apply some nice OpenCV filter to obtain a transformed video stream line in the movie Terminator. :-)
    • Use one button to trigger the video recording. Use a blinking LED to let known that it is "On Air".
    • ...

    Recording movies with the camera

    Recording a movie with OpenCV can be done in less than 25 python lines. It works well with my old Logitech C170 but for some reasons it did not work out of the box with my Microsoft LifeCam Studio. Dear visitor, if you have such a camera, here the magic trick to produce your new feature movie ! First, make sure to have this model with the lsudb command:

    Bus 001 Device 007: ID 045e:0811 Microsoft Corp. Microsoft® LifeCam Studio(TM)

    The camera produce naturally a MJPG stream. I would sum it up a stream of JPEG pictures. By default, the VideoWriter class will produce empty video files. Unfortunately, by default there are no debug message to help you. Don't forget to use the following environment variables during your hacking sessions:


    To make it work, you need to tune the camera settings before obtaining the desired result. The complete program is displayed here. Follow the comments to see where the magic happens.

    import cv2
    import os
    cap = cv2.VideoCapture(0)
    if not cap.isOpened():
        raise IOError("Cannot open webcam")
    # Magic number corresponding to a MJPG Stream
    codec = 0x47504A4D  
    # You actually says that your camera produces such a stream
    cap.set(cv2.CAP_PROP_FOURCC, codec) 
    # We fix the resolution, the framerate and use exactly the same in the VideoWriter arguments    
    cap.set(cv2.CAP_PROP_FRAME_WIDTH, 640)  
    cap.set(cv2.CAP_PROP_FRAME_HEIGHT, 480)
    # The framerate is not limitating here
    cap.set(cv2.CAP_PROP_FPS, 20.0)     
    # next we define the filename, the writer options and start the infinite loop.
    videoname = os.path.join('/tmp/', f"output.avi")
    fourcc = cv2.VideoWriter_fourcc(*'MJPG')
    video_writer = cv2.VideoWriter(videoname, fourcc, 20.0, (640, 480))
    while True:
        ret, frame = cap.read()
        # When the Q key is pressed, the loop is stopped
        if cv2.waitKey(1) & 0xFF == 27:

    Webserver configuration

    You can find here the webserver and uWSGI configurations used to make it work.


    upstream mjpeg {
    server {
      listen 443 ssl;
      server_name namek.agayon.netlib.re;
      location / {
      proxy_redirect off;
      proxy_pass http://mjpeg;
      index index.html;
      location /api {
        include uwsgi_params;
        proxy_read_timeout 300s;
      location /static/ {
        alias /srv/http/ngnix/r1d3/public_html/static/;
        try_files $uri $uri/ /static/lost_bot.jpg;
       ssl_certificate     /etc/letsencrypt/agayon.netlib.re_fullchain.pem;
       ssl_certificate_key /etc/letsencrypt/agayon.netlib.re.key;
       ssl_session_timeout 1d;
       access_log /var/log/nginx/r1d3.access.log;
       error_log /var/log/nginx/r1d3.error.log;
       error_page 500 502 503 504 /500.html;
       location = /500.html {
           root   /srv/http/ngnix/r1d3/errors;
           allow all;
       proxy_read_timeout 720s;
       proxy_connect_timeout 720s;
       proxy_send_timeout 720s;
       proxy_set_header X-Forwarded-Host $host;
       proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
       proxy_set_header X-Forwarded-Proto $scheme;
       proxy_set_header X-Real-IP $remote_addr;


    chdir = /srv/http/ngnix/api/rest_api/
    processes = 4
    threads = 2
    plugin = python
    virtualenv = /srv/http/ngnix/api/rest_api/venv
    module = api_agayon.agayon_app:app
    callable = app
    wsgi-file = wsgi.py
    master = true
    socket =
    ;route-uri = ^/api/(.*) rewrite:/$1
    vacuum = true
    die-on-term = true
    kill-on-idle = true
    wsgi-file = wsgi.py
    stats =


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  3. A remotely controlled mapping device

    Published: Sun 05 January 2020
    Updated: Sun 05 January 2020 By Arnaud In Agayon. tags: agayon

    During the Christmas holidays, I took the time to work on the Agayon. I hope that the mechanical parts are almost finished and I will be able to focus on the code in the following weeks/months.

    Do as you’re told

    A few years ago, I have been gifted with a PS4 controller to play on my Retropie Setup. These are quality controllers but Sony does not like makers. My model cannot be used with vanilla bluetooth drivers on my Pie. And for unknown reasons, the alternative driver ds4drv does not works for me. I purchased a 5m USB mini cable to not disappoint my lovely niece and nephew. They can plan with Supertuxkart for hours. But it's not the subject of this article. I plan to use the Agayon not only in my apartment but also to go on tour with it ! (let's dream a bit). Unfortunately, it is already quite heavy and it could be cool to drive it from my door to the car. I could dream again and imagine a system where it recognize me after a little bit of training like a dog or a case. It seems possible but why not use the controller at first. It should be easier and quick to implement. Moreover, the kids and friends seems to love the idea. So let's do it ! I will keep you updated when it is reliable and easy to use.

    Back to the future remote Photo credit: Back to the Future (1985)

    Re-verify our range to target... one ping only

    I have finally mounted the Lidar on the Agayon. The Raspberry Pi 2 was too slow to handle the data but the Pi 4 does well the job.

    Mounted lidar

    My living room

    The following animation has been made with the animate.py script from the RPLIDAR repository. lidar animation polar coordinates


    Last year I discovered the Raznot project and it inspired me. According to the readme, the RazTot is an easy DIY project which allows you to remotely control a roving security camera securely from your browser. After some tests, I decided to not use this project because the flask server and interface would not so nicely integrate with my R1D3 base code. I only use Janus Janus, a general purpose WebRTC server to stream from the robot in a generic web page for now. Unfortunately, my Microsoft LifeCam Studio does not produce a stream compatible with Janus. I need to transcode the MPEG-4 video stream to H264 with ffmpeg to see it in a browser. I hope to be able to release the code in the following weeks.

    More to come, stay tuned !

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  4. New Converse plugin: Verify HTTP requests with XMPP

    Converse is a JavaScript XMPP client that can be run in a web browser. Unfortunately, it does not support the XMPP extension (XEP) that allows to verify HTTP Requests via XMPP (XMPP): XEP-0070. So I decided to code a small plugin to provide this functionality.

    This article follows the serie about this XEP:


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