i have a webserver application using PHP, this application have to send 200MB of data to every device connected to the local network using wifi (Devices are a minimum of 100 to 300). I can send it using a ZIP file (200MB) or sending every single file (from 1 to 10 MB for each file).
Actually i have used TCP protocol on a very good hardware and all works very good! but now, i have to send it using a raspberry Pi 2..
what is the best protocol to do it? I can use a multicast approach? someone know the best way for do it on a raspBerry? I need this operation takes a very short time ;)
ps: For wifi network i have a very good antenna and i can link my raspeberry to the router using cable.
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I'm using a LPC178 development board and I want to read a file present on a Windows PC. My dev board only has a RS2323 interface to communicate with.
How can I go about transferring the file from my PC to my MCU using a RS232 (serial) link? I found a reference which explains how to transfer data between a MCU and PC but it isn't about file transfers.
Afaik there is no easy solution for this like calling something like "copy" or "fopen" over RS232. I would be happy to be proven wrong here.
The fastest solution might be to write a little programm running on your Windows Host, which listens to your RS232 communication and pipes your communication into/out of the file based on your communication protocol. This can be done with standard file operations in the language of your choice, for example C, C++ or Python.
Your problem is one of the oldest in the book. How do you transfer files without fancy operating system abstractions. For RS232 (or any other serial method) there exists many file transfer protocols.
One of them is kermit. This is a protocol from 1981 and can transfer binary and text files. It is able to be embedded in a micrcontroller and there exists programs to transfer/receive using kermit.
alternative old site for reference
In the simplest case you would use a file transfer protocol such as XMODEM, YMODEM, ZMODEM or Kermit - these protocols were designed in the days before networking and the Internet were ubiquitous and deal with simple point-to-point transfers between two computers. They are supported bu most terminal emulator tools such as TeraTerm Pro or PuTTY so no specific PC software need be written, just the microcontroller end.
A more complex but flexible solution is to implement a TCP/IP stack and a PPP driver, and an FTP application layer - probabaly only practical if using a third-party TCP/IP stack and application layer. You can then use any FTP client for the PC end, so again no PC software required. While this may be overkill if all you need to do is transfer files, it has the advantage of allowing you to use the the single serial port concurrently for other data streams and application protocols such as Telnet. The disadvantage perhaps is that while Windows does support PPP it is buried within the dial-up networking and to be frank a pain to get working.
Very first step you have to do is ensure serial communication is working fine.
Send a byte continuously from mcu to PC and display it on some io console (for example: HyperTerminal, Dock light )
Receive a byte to mcu from PC and echo it back to PC.
Once you are sure that serial communication is working fine then select some file transfer protocol and implement it.
While you can select any of the available protocols or write your own protocol and implement it.
For purpose of discussion i select Xmodem protocol.
If you consider some other protocol you may stop reading answer here.
XMODEM is a simple file transfer protocol.
Refer http://web.mit.edu/6.115/www/amulet/xmodem.htm for detailed information.
You may implement Xmodem mcu side by reading protocol. Or may consider using open source also ( if available )
PC side i prefer to use HyperTerminal io console as it is compatible with Xmodem.
In HyperTerminal all that i have to do is configure settings and select file for transfer to mcu.
Now transfer any file to mcu using Xmodem protocol from PC.
What you do with received file in mcu is up to you : )
I am working on creating a touch pad device (custom hardware but similar to an android device) that acts as a touchscreen drawing pad similar to the Wacom Bamboo drawing pads. However, the key feature of the device is instead of connecting it to the computer with wires or via Bluetooth, it connects to the local WiFi network and searches for devices with a port open (currently 5000 for testing purposes). Currently, I have a client written in C that when launched opens up a DatagramSocket on port 5000 and waits for a custom UDP packet containing normalized X, Y, and pressure. Then, for testing purposes, I am putting the normalized X and Y into SendInput. SendInput "works" however injecting packets into the computers current mouse is not what I want. Instead, I want to have it considered as a seperate input device so programs like gimp will be able to detect it and assign custom functions based on the data (ie: have gimp utilize the pressure data).
The problem is I dont know where to start to create a driver that does the former. I have been extensively looking at the winddk thinking that might be the key. The problem with the winddk is I cannot find any documentation on creating a HID driver using data that is not from a ps/2 or usb. This tutorial got me thinking about using IOCTLs, but I am not really sure how to make them be considered as input.
As a side note, in the title I said TCP/UDP because I am willing, and considering for security purposes, to change from UDP connection to TCP.
If someone can push me in the right direction or link me to some related documentation and samples, that would be awesome because right now I am lost. Thank you.
I want to send data packets into the network bypassing the Linux network stack. I mean is there any way where I can interrupt the network card driver and place a frame in the network card buffer directly to send it in the network? I am a newbie in Linux Kernel hacking so any guideline on how I can get started will be very helpful.
You would be better off if you used some virtual device like TAP. You can easily hack a control interface into the TAP kernel module, via which you can then pass frames ready to be sent out to the driver. That approach can be compared to the performance of a regular socket application as the baseline. Since in the end the TAP device will "send" out egress frames via a character device, you can easily write a test application measuring performance and latency.
I am doing some projects with Arduino at the moment, and I was wondering if it is possible to make HTTP requests without the Internet shield.
The idea was to make a program which does HTTP requests and sends the response to the Arduino over the serial port.
I did some search online, but I could not find a way how to send the response to the Arduino board.
Yep, I've done this. I had a remote temperature logger built with an Arduino. Then I used the USB cable to connect the Arduino to a laptop. The laptop had a WiFi connection to my network and could get out to the Internet if it wanted to, but I actually just connected to my desktop.
I didn't do anything special on the Arduino other than writing to/reading from the Serial port. I had a tiny Python program on the laptop acting as a gateway to the network (read from Serial, write to port and vice versa) and another tiny Python program on my desktop to read from port and write to disk.
it is possible also to use pyfirmata in a python web server like flask under linux to control your arduino via web interface.your arduino will commnunicate with your web server via firmata protocol
I've come across an interesting problem. Basically I have 2 mobile phones that are both behind NATs. I want to communicate directly between the 2 devices using UDP.
I know if I initiate a connection from the phones to a server then I can push data back down that connection to the phone (ie send it back from the same port that received the message to the same ip and port that it was received from). So I can easily communicate between the 2 devices by connecting both phones to the server. Then sending data to the server and having it re-routed back to the phones. This bypasses any NAT traversal issues I may come up against.
However I would rather just use the server to point the 2 devices at each other and then let them communicate directly. How would I go about doing this? Is it possible without using something like uPnP?
Any help would be much appreicated!
Edit: I found this document http://www.brynosaurus.com/pub/net/p2pnat/ It looks like hairpin translation is what I'm after but it doesn't look to be widely supported. I wonder how good mobile ISP's support for UPnP is?
What you're looking for is UDP hole punching, see e.g. http://en.wikipedia.org/wiki/UDP_hole_punching
The basic idea is simple, you tell each endpoint the ports to use, and they start sending udp packets. The NAT'ing devices will set up a traversal rule when they see the first outgoing packet, and then the next attempt from the other end will match this traversal rule.
You need a mediator server, so the clients can tell where they are. Then one opens a server by uPNP, and the other connects to it.