Sorry if it has been asked before but I cannot find anything on the internet. I just want to host a page in arduino ethernet shield and when I visit it from a browser with Get parameters (e.g http://xxx.xxx.xx.xx/led.html?red=255,green=0,blue=255) to change to change the led's color. I cannot find how to send data from browser to arduino.
The answer involves the use of The Ethernet Library (Ethernet.h) - which provides an interface to Client and Server, a degree of conceptualizing low-level I/O and buffering the input, and context.
In the following code snippet ( of the sample code at http://arduino.cc/en/Tutorial/WebServer )
...
char c = client.read();
Serial.write(c);
...
the line char c = client.read() is taking a byte from the request stream and assigning it to a char type, it is then serialing that charbyte to a string where it perform conditional logic on it.
The conditional logic of that sample only cares about reading whether a return character \n on a blank line, but the bytes that are being read (on each iteration) byte to byte, actually compose the RAW Request.
At minimal, a RAW HTTP GET Request looks like this:
GET /?first=John&Last=Doe HTTP/1.1
Host: localhost
So, for you to read the query string, you'll need to buffer the bytes being read from the stream.
Then, you'll likely serialize the whole buffer into a string, and perform string operations on them, as well as your conditional logic....
Related
I am building a web server from an ESP8266 that will send environmental data to any web client as a web page. I'm using the Arduino IDE.
The problem is that the data can get rather large at times, and all of the examples I can find show assembling a web page in memory and sending it all at once to the client via ESP8266WebServer.send(). This is ok for small web pages, but won't work with the amount of data I need to send.
What I want to do is send the first part of the web page, then send the data out directly as I gather it, then send the closing parts of the web page. Is this even possible? I've looked unsuccessfully for documentation and there doesn't seem to be any examples anywhere.
For future reference, I think I figured out how to do it, with help from this page: https://gist.github.com/spacehuhn/6c89594ad0edbdb0aad60541b72b2388
The gist of it is that you still use ESP8266WebServer.send(), but you first send an empty string with the Content-Length header set to the size of your data, like this:
server.sendHeader("Content-Length", (String)fileSize);
server.send(200, "text/html", "");
Then you send buffers of data using ESP8266WebServer.sendContent() repeatedly until all of the data is sent.
Hope this helps someone else.
I was having a big issue and a headache in serving big strings concatenating together with other strings variables to the ESP32 Ardunio webserver with
server.send(200, "text/html", BIG_WEBPAGE);
and often resulted in a blank page as I reported in my initial error.
What was happening was this error
E (369637) uart: uart_write_bytes(1159): buffer null
I don't reccommend to use the above server.send() function
After quite a lot of reaserch I found this piece of code that simply works like a charm. I just chunked my webpage in 5 pieces like you see below.
server.sendHeader("Cache-Control", "no-cache, no-store, must-revalidate");
server.sendHeader("Pragma", "no-cache");
server.sendHeader("Expires", "-1");
server.setContentLength(CONTENT_LENGTH_UNKNOWN);
// here begin chunked transfer
server.send(200, "text/html", "");
server.sendContent(WEBPAGE_BIG_0);
server.sendContent(WEBPAGE_BIG_1);
server.sendContent(WEBPAGE_BIG_2);
server.sendContent(WEBPAGE_BIG_3);
server.sendContent(WEBPAGE_BIG_4);
server.sendContent(WEBPAGE_BIG_5);
server.client().stop();
I really own much to this post. Hope the answer hepls someone else.
After some more experiments I realized it is faster and more efficient the code if you do not feed the string variable into the server.sendContent function. Instead you just paste there the actual string value.
server.sendContent("<html><head>my great page</head><body>");
server.sendContent("my long body</body></html>");
It is very important the when you chunk the webpage you don't chunk html tags and you don't chunk an expression of a javascript code (like cutting in half a while or an if), while chunking scripts just chunk after the semicolon or better between two function declarations.
Chunked transfer encoding is probably what you want, and it's helpful in the situation where the web page you are sending is being dynamically created on-the-fly and is also too large to fit into memory. In this situation, you have two problems. One, you can't send it all at once, and two, you don't know ahead of time how big the result is going to be. Both problems can be fixed like this:
String webPageChunk = "some html";
server.setContentLength(CONTENT_LENGTH_UNKNOWN);
server.send ( 200, "text/html", webPageChunk);
while (<page is being generated>) {
webPageChunk = "some more html";
server.sendContent(webPageChunk);
}
server.sendContent("");
Sending a blank line will tell the client to terminate the session. Be careful not to send one in your loop before you're done generating the whole page.
I am reading sensor data and I need to send these data via bluetooth so I am using noble/bleno library to subscribe data every time the value change. Here I am confusing how to send data as a buffer.
I have data something like value = 24.3756
So I need to write this in buffer:
let buf = new Buffer(2);
buf.writeIntLE(buf);
But when I convert to ArrayBuffer value shows only 24 (not getting after decimal point)
How to send full float value and read as array buffer ?
First of all please read Buffer documentation here.
Then please don't use deprecated functions. If you need to create a new buffer use Buffer.alloc or Buffer.allocUnsafe. When you're creating buffer ensure that it can hold the data you want to write there. Next please use a suitable method for writing data. You're writing floating point number, then you have to use Buffer.writeFloatBE/Buffer.writeFloatLE. If you do everything I mentioned you'll end up with a correct solution:
const buffer = Buffer.allocUnsafe(4);
buffer.writeFloatLE(24.3756);
I am trying to write my first big Arduino Library, in this case to control the ESP8266.
I would like to pass as parameter the WEBSITE address to a method that will do the GET request so I need to send two long Strings:
(1) Fix part of the website url
(2) json with the data to add to
the request
1) The fix part is this:
#define WEBPAGE "/mywebsiteURLfolder/post.php?json={"
So I call my library method:
myESPinstanceSOFT.Send_OnlineService(1, HOST, WEBSITE, 9);
And my library should receive it and use to create a final String that will be used to send it via Serial to the ESP8266:
bool ESP8266Class::Send_OnlineService(byte type, String HOST, String WEBPAGE, int Node_ID){
String request = "GET ";
request += WEBPAGE;
request += "Node_ID:";
etc etc
Given that WEBSITE is a fix string. How can I save it in flash and just point to it when constructing the request string?
Thank you very much
I just recently started working with Arduino. I just have a quick question, I tried searching for an answer but have failed for days. Basically what I wanna ask is if there is a way to read a whole line from the Serial Port. Like the line highlighted in the picture below.
What I'm trying to do is using a Bluesmirf Silver Rn-42 to search the area for a bluetooth device and trigger a signal if a matching address is found. I just cant figure out how to read messages that are already on the Serial port.
Use .readString()
Example code:
String myString;
void setup()
{
Serial.begin(9600);
}
void loop()
{
while (Serial.available())
{
myString = Serial.readString();
//do stuff with the string
}
}
If you want to read something that's already in the serial port from the Arduino end, then you need to rethink your code. Anything you produce within your code to print to the serial monitor will already be in your program ready to access if you make it available in the right way. The exemplar string you provided, is simply an array of characters that you can store in an element within an array, making it accessible whenever you need it.
Hints:
Never read back from the serial monitor, it's really slow -.-
Make all the resources you require accessible and available in memory at the time you need it to save hassel & processing power.
Never make the same mistake twice.
However, if you want to read from the COM port that the Arduino is connected to in Windows, then you'll need to work with Libusb libraries found here: http://www.libusb.org/ for C. Any other language will be library or import dependent.
I'm writing code to send raw Ethernet frames between two Linux boxes. To test this I just want to get a simple client-send and server-receive.
I have the client correctly making packets (I can see them using a packet sniffer).
On the server side I initialize the socket like so:
fd = socket(PF_PACKET, SOCK_RAW, htons(MY_ETH_PROTOCOL));
where MY_ETH_PROTOCOL is a 2 byte constant I use as an ethertype so I don't hear extraneous network traffic.
when I bind this socket to my interface I must pass it a protocol again in the socket_addr struct:
socket_address.sll_protocol = htons(MY_ETH_PROTOCOL);
If I compile and run the code like this then it fails. My server does not see the packet. However if I change the code like so:
socket_address.sll_protocol = htons(ETH_P_ALL);
The server then can see the packet sent from the client (as well as many other packets) so I have to do some checking of the packet to see that it matches MY_ETH_PROTOCOL.
But I don't want my server to hear traffic that isn't being sent on the specified protocol so this isn't a solution. How do I do this?
I have resolved the issue.
According to http://linuxreviews.org/dictionary/Ethernet/ referring to the 2 byte field following the MAC addresses:
"values of that field between 64 and 1522 indicated the use of the new 802.3 Ethernet format with a length field, while values of 1536 decimal (0600 hexadecimal) and greater indicated the use of the original DIX or Ethernet II frame format with an EtherType sub-protocol identifier."
so I have to make sure my ethertype is >= 0x0600.
According to http://standards.ieee.org/regauth/ethertype/eth.txt use of 0x88b5 and 0x88b6 is "available for public use for prototype and vendor-specific protocol development." So this is what I am going to use as an ethertype. I shouldn't need any further filtering as the kernel should make sure to only pick up ethernet frames with the right destination MAC address and using that protocol.
I've worked around this problem in the past by using a packet filter.
Hand Waving (untested pseudocode)
struct bpf_insn my_filter[] = {
...
}
s = socket(PF_PACKET, SOCK_DGRAM, htons(protocol));
struct sock_fprog pf;
pf.filter = my_filter;
pf.len = my_filter_len;
setsockopt(s, SOL_SOCKET, SO_ATTACH_FILTER, &pf, sizeof(pf));
sll.sll_family = PF_PACKET;
sll.sll_protocol = htons(protocol);
sll.sll_ifindex = if_nametoindex("eth0");
bind(s, &sll, sizeof(sll));
Error checking and getting the packet filter right is left as an exercise for the reader...
Depending on your application, an alternative that may be easier to get working is libpcap.