This is a theorical question. I have no code and I am not looking for that, just knowledge.
I have a raspberry pi with a webserver and a waveshare can-hat. It receives various messages from a dozen devices.
among those messages a few contains data (some informations are divided over multiple messages).
My idea is to receive the messages, restore complete informations and write one file each.
then an ajax call reads each file and displays each value in the webpage. Probably once every second.
Is it possible to do that? is there a better way?
the receiving script will be made in C.
thank you for helping and sharing your knowledge!
I think it would be a better practice if you create some kind of process (or some kind of kernel module or daemon for example) which read out the data from CAN and you use this process with Python and use some sort of Webserver-API to display the data via web.
You can find some ideas for IPC between a C and a Python application here.
So one simple solution would be to create a socket system with a C guest and a Python master. Your Python application is a flask application which waits for a connection of the C application (or vice versa) and the C application transmit all incomming data to your Python application.
This would be a more neat solution than writing and reading a file.
Related
I'm trying, finally, to understand eBPF and maybe use it in an upcoming project.
For sake of simplicity I started with reading bcc documentation.
In my project I'll need to send some data over network upon some kernel function calls.
Can that be done without sending the data to userspace first?
I see that I can redirect skbs from one socket to another etc., and I see that I can submit custom data to user space. Is there a way to get the best of both worlds?
EDIT: I'm trying to log some file system events to another server that'll collect this data from multiple machines. Those machines can be fairly busy in some situations. It should be real time and with low latency.
I'd love to avoid going through userspace to prevent copying the data back and forth and to reduce sw overhead as much as possible.
Thank you all!
It seems this question can be summarized to: is it possible to send data over the network from a BPF tracing program (kprobes, tracepoints, etc.)?
The answer to that question is no. As far as I know, there are currently no way to craft and send packets over the network from BPF programs. You can resend a received packet to the network with some helpers, but they are only available to networking BPF programs.
I want to write a Forth program for my Raspberry Pi. This program shall read some sensor data from an existing file and send it to a website where the data gets stored.
Searching the web there was plenty of documentation about how easy and fast Forth is and how to calculate Fibonacci numbers. But how can I request a URL? How can I send data to a website and process the result?
If there's no socket support: is it possible to start an external program like curl/wget to do the request?
It is not obvious from the question what the Forth implementation is used.
For example, Gforth (that is available on Raspberry Pi)
has some support of the sockets and also it allows to start an external program using system word. See my answer on the similar question: How do I read raw code from a website in Gforth?
Example of creating curl child process in Gforth:
S" curl https://example.com/" system
In any case,
it seems that the most promising approach for the given problem is to develop a binding to libcurl (if it doesn't exist yet for the used Forth implementation).
I need to stream data from a web server to clients. The data is location data that is collected and stored on the server. The clients will click a button on an html page to 'opt in' to start receiving the data. This data is never ending and there is at least one of the clients that needs to receive the data 24-7, with as few breaks as possible. The data being streamed will be client specific, as each client wont receive the exact same data.
I've done several multi-threaded tcp servers over sockets, and websockets are the way I would like to attack this, but the requirements are that this has to work in ie9.
The initial requirement was that this be a vb.net cgi executable - but during testing, I havent been able to 'use' the stream from the vb.net executable until the app finishes - like it wasn't able to flush the stdout even though I was specificly using the console.out.flush(). So If this isn't a viable option, and I can support this with facts, then I can get this requirement changed.
I've also read quite a bit about using a third party server to stream the data like Orbit and APE I think was a couple of them, but requirements are for 1 server - the web server. No other hardware can be required.
I'm pretty sure the vb.net CGI isn't the ideal solution based on what i've found, but is it doable or do I need to abandon that solution and move on to a newer technology , ISAPI? Any ideas or suggestions, even if they just point me in the right direction, are greatly appreciated.
You might go few ways.
If you would go C# .Net, then you might look into Silverlight solution. But it requires plugin in browser to be installed (like Flash). Good thing here, is that you are able to send data through normal sockets, in pure realtime from server. In same time Silverlight uses .Net so it makes some code to be shared. That helps development process. As well the way it will work in different browsers will be same.
You might have a look in similar solution using Java Applet with Java backend (can be even .Net, but again, easier to develop when both in same language).
Another option is to have fron-end using WebSockets, but as you know its not supported in IE9 and below (IE10 promises to be), and Opera is not supporting it as well.
Backend can be done in what you prefer. But bear in mind that WebSockets uses framing, and for constant but little packets its not efficient, because if you send 10 bytes, then it will create frame 2-12 bytes, and TCP packet header that is 40 bytes in average.
To support older browsers you might have a look in long-polling, but it is not as reliable as websockets.
As well it is important to calculate the amount of data and approximate amount of users that will use your system. Based on calculations you will have approximate information about how real it is, and what server will be required to handle.
How can i connect a windows phone 7 device with a WiFi-enabled micro controller. Should i use socket programming?? If yes then how?? I actually want to send a text file or a text message to the micro controller using WI-FI??
Your question is a bit vague. Are you trying to write a app that enables you to send a text file/message?
or are you trying to accomplish this by connecting to the microcontroller with the default connection your phone provides.
If you want to write your own app, you can do this by using a windows socket function. Have you looked into the standard code examples windows provides? They provide good examples about the basis of windows phone wifi connectivity
in example:
Example 1
Example 2
Edit:
You should take a look at this example.
Example
In this microsoft example, they make the game tic tac too between two windows phones. For your cause, you can read the data form file. Temporarly store it in an array. And send it over wifi. if you customize the example to fit your needs, so in steps:
Declare a socket (with the right ip adresses, ports etc)
Read file
Store in array
Send array by the wifi (using your previously declared socket)
And then on the microcontroller, you need some way to filter your data out of the incomming wifi buffer. I looked into one of my older projects where i did something like this. But i couldn't find it anymore. So i must have deleted it at some point "sorry :( " i you can work this out using the example
I am looking for advice/guidance on how to achieve the following:
I have a circuit mounted and connected to an Arduino and I am able to easily retrieve data from it, using Python and the pySerial module. It allows me to determine the value of an analog input over time.
At the moment I am storing that data to a file, with a time stamp and the correspondent value and I would love to hear opinions and thoughts on how I could 'share' this data to a web server and 'play' it live.
Is it possible to 'stream' the values into the dump file and retrieve data from it at the same time through an AJAX request or should I look into event-driven web servers like 'Tornado', 'Twisted'...
I am a bit lost here. Just for the record, I am comfortable with PHP and JavaScript for the final output, I just don't have a clue on how to constantly 'stream' the data I need.
Thanks in advance.
If you don't plan to update the Ardunio device too much then it would make sense to have the Python component continue to collect the data over the serial port and publish it in a way that can easily be consumed by a service which can distribute the information in a more efficient, and probably flexible, manner.
e.g.
read the data from the serial port and publish messages onto a message queue. The message queue can then be read by any other component and the data can then be distributed to other applications/clients.
Make a web call to a server that can process each update and distribute to other applications/clients.
You could use something like Pusher (who I work for) and make a call to the REST API to deliver each message to any connected clients. Whilst this is a good way of distributing your data you will be publishing your data even if no clients are listening so I think you are best to get the data to a component like a web server first.
Assuming you go with 1 or 2, you can then use realtime web solution to distribute the data to any number of clients. You could use Pusher here or you could use a self hosted solution.
So, the data flow as I see it would be:
Ardunio -> small Python app -> Queue (or HTTP request to Web server) -> Realtime Web Technology -> Many clients