let's assume that there is a website under HTTPS, in that WebSite the user can set the IP of a local machine (thermal printer in this case). How can the user print something on that printer by using the website from his device?
The user have to use the WebSite only under the local network where the thermal printer is to be able to print.
The printer has a http server in it which it uses for the communication.
At this point how can a HTTPS website send a HTTP request to that local thermal printer?
Assuming you want this to be a variable that any user inputs,and that any user on any network has the ability to access their own printer, you would need it to be executed on the frontend. This way each user will be able to access the printer on their own network.
That gives you basically one option. Javascript. So if you wanted a stored request with some variables, you could have the javascript store variable from the DOM and then post a fetch request https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/Using_Fetch
Here is an example function
// Example POST method implementation:
async function postData(url = '', data = {}) {
// Default options are marked with *
const response = await fetch(url, {
method: 'POST', // *GET, POST, PUT, DELETE, etc.
mode: 'cors', // no-cors, *cors, same-origin
cache: 'no-cache', // *default, no-cache, reload, force-cache, only-if-cached
credentials: 'same-origin', // include, *same-origin, omit
headers: {
'Content-Type': 'application/json'
// 'Content-Type': 'application/x-www-form-urlencoded',
},
redirect: 'follow', // manual, *follow, error
referrerPolicy: 'no-referrer', // no-referrer, *no-referrer-when-downgrade, origin, origin-when-cross-origin, same-origin, strict-origin, strict-origin-when-cross-origin, unsafe-url
body: JSON.stringify(data) // body data type must match "Content-Type" header
});
return response.json(); // parses JSON response into native JavaScript objects
}
postData('https://example.com/answer', { answer: 42 })
.then(data => {
console.log(data); // JSON data parsed by `data.json()` call
});
You are likely struggling because of CORS.
You can find in depth discussion here https://javascript.info/fetch-crossorigin
In short, you will need to modify the fetch headers to have the correct credentials, mode, etc. as seen in the comments in the above snippet.
I use Vuejs to create my frontend for my project.
At the creation of one component ('TimeCapsy.vue'), I make an AJAX call to my backend like this:
created: function () {
if (verify.verify_login()) {
let token = this.$cookies.get('jwt_us_cas');
let params = {'jwt': token};
console.log(params);
axios({
method: 'post',
url: dev.HOST+'getuserinfoobject',
params: queryString.stringify(params)
})
.then(response => {
console.log(response.data)
})
}
}
As you can see I use the
this.$cookies.get('jwt_us_cas');
to get the a json web token, that I set on the client at the login.
I use the queryString Library to stringify my parameters for my request.
I also tried it without the queryString.stringify(params) call, but I get the same error, e.g. the parameter still turns into null.
When I look at the console log, where I check the params variable, I get this output:
{jwt: "my token comes here"}
So I can see, that it gets the correct value from the cookie.
But when I check the answer from my backend (PHP), I get this error:
Undefined index: jwt in <b>D:\casb\public\index.php</b> on line <b>52</b>
Of course I know that it means, that jwt is null, but I can't understand why.
As I said, right before I make the call I check the params and it shows the token.
I checked the endpoint with Postman and the token as the jwt parameter and it returned a successfull call with the correct answer.
A correct answer is basically just a nested object with some information in it.
My PHP endpoint is pretty basic too:
Router::add('/getuserinfoobject', function () {
$response['response'] = User::getUserInfoObject($_POST['jwt']);
echo json_encode($response);
}, 'post');
So I guess that right before or in my call it nulls my parameter. But I can't understand how, since I make a lot of requests and never had this problem.
From axios docs
params are the URL parameters to be sent with the request
Which means, you should get the value with PHP $_GET.
Or $_REQUEST (which stores both $_GET, $_POST. Also $_COOKIE).
The other hand, you can use data key as docs says
data is the data to be sent as the request body
Only applicable for request methods PUT, POST, and PATCH
So the value would be available in $_POST
axios({
method: 'post',
url: dev.HOST+'getuserinfoobject',
data: {
jwt: token
}
})
again, I got another problem with casperjs, now with sendAJAX function.
It says that sendAJAX has 5 parameters which are these followings :
url: The url to request.
method: The HTTP method (default: GET).
data: Request parameters (default: null).
async: Flag for an asynchroneous request? (default: false)
settings: Other settings when perform the AJAX request (default:
null)
So, it says the data method is object so, it should be filled with :
var data = new Object();
data.amount= 15;
and also with this one,
var data = {amount:15};
but there were no successful value send to my web service (always send 0 as value, but ajax request successful, even returning the json data) which has an url like this
"http://localhost:9000/TempCountryAmountREST/setCountryAmount"
It will be succeed if I direct bind my data variable to my url like this :
"http://localhost:9000/TempCountryAmountREST/setCountryAmount?amount="+amount
[UPDATE]
The TempCountryAmountREST is my controller name and setCountryAmount is my function inside my controller.
[UPDATE]
I forgot to include my usage of sendAJAX(), here is the code that I use :
return JSON.parse(__utils__.sendAJAX(wsurl, "POST" , data, false, { contentType: "application/json" }));
So how does I fill the data in the sendAJAX parameter?
Thanks in advance...
Sorry, I've found what the answer is.
I make some mistakes in contentType which I was set with contentType: "application/json" instead of contentType: "application/x-www-form-urlencoded" }
If we are looking about how ajax send the content from method send(), they were use x-www-form-urlencoded. See this for more detail
When we see through casperjs clientutils.js script, we should found how sendAJAX work.
On the `this.sendAJAX = function sendAJAX(url, method, data, async, settings) {
}
there are url construction logic which transformed our Object (if so) to x-www-form-urlencoded form. So that we need to set our contentType as application/x-www-form-urlencoded
Very well, thanks for your attention...
Having trouble with what I thought was a relatively simple jQuery plugin...
The plugin should fetch data from a php script via ajax to add options to a <select>. The ajax request is pretty generic:
$.ajax({
url: o.url,
type: 'post',
contentType: "application/x-www-form-urlencoded",
data: '{"method":"getStates", "program":"EXPLORE"}',
success: function (data, status) {
console.log("Success!!");
console.log(data);
console.log(status);
},
error: function (xhr, desc, err) {
console.log(xhr);
console.log("Desc: " + desc + "\nErr:" + err);
}
});
This seems to work fine in Safari. In Firefox 3.5, the REQUEST_TYPE on the server is always 'OPTIONS', and the $_POST data does not appear. Apache logs the request as type 'OPTIONS':
::1 - - [08/Jul/2009:11:43:27 -0500] "OPTIONS sitecodes.php HTTP/1.1" 200 46
Why would this ajax call work in Safari, but not Firefox, and how do I fix it for Firefox?
Response Headers
Date: Wed, 08 Jul 2009 21:22:17 GMT
Server:Apache/2.0.59 (Unix) PHP/5.2.6 DAV/2
X-Powered-By: PHP/5.2.6
Content-Length 46
Keep-Alive timeout=15, max=100
Connection Keep-Alive
Content-Type text/html
Request Headers
Host orderform:8888
User-Agent Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.5; en-US; rv:1.9.1) Gecko/20090624 Firefox/3.5
Accept text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language en-us,en;q=0.5
Accept-Encoding gzip,deflate
Accept-Charset ISO-8859-1,utf-8;q=0.7,*;q=0.7
Keep-Alive 300
Connection keep-alive
Origin http://ux.inetu.act.org
Access-Control-Request-Method POST
Access-Control-Request-Headers x-requested-with
Here is a picture of the Firebug output:
The reason for the error is the same origin policy. It only allows you to do XMLHTTPRequests to your own domain. See if you can use a JSONP callback instead:
$.getJSON( 'http://<url>/api.php?callback=?', function ( data ) { alert ( data ); } );
I used the following code on Django side to interpret the OPTIONS request and to set the required Access-Control headers. After this my cross domain requests from Firefox started working. As said before, the browser first sends the OPTIONS request and then immediately after that the POST/GET
def send_data(request):
if request.method == "OPTIONS":
response = HttpResponse()
response['Access-Control-Allow-Origin'] = '*'
response['Access-Control-Allow-Methods'] = 'POST, GET, OPTIONS'
response['Access-Control-Max-Age'] = 1000
# note that '*' is not valid for Access-Control-Allow-Headers
response['Access-Control-Allow-Headers'] = 'origin, x-csrftoken, content-type, accept'
return response
if request.method == "POST":
# ...
Edit: it seems to be that at least in some cases you also need to add the same Access-Control headers to the actual response. This can be a little bit confusing, since the request seems to succeed, but Firefox does not pass the contents of the response to the Javascript.
This mozilla developer center article describes various cross-domain request scenarios. The article seems to indicate that a POST request with content type of 'application/x-www-form-urlencoded' should be sent as a 'simple request' (with no 'preflight' OPTIONS request). I found , however, that Firefox sent the OPTIONS request, even though my POST was sent with that content type.
I was able to make this work by creating an options request handler on the server, that set the 'Access-Control-Allow-Origin' response header to '*'. You can be more restrictive by setting it to something specific, like 'http://someurl.com'. Also, I have read that, supposedly, you can specify a comma-separated list of multiple origins, but I couldn't get this to work.
Once Firefox receives the response to the OPTIONS request with an acceptable 'Access-Control-Allow-Origin' value, it sends the POST request.
I've fixed this issue using an entirely-Apache based solution. In my vhost / htaccess I put the following block:
# enable cross domain access control
Header always set Access-Control-Allow-Origin "*"
Header always set Access-Control-Allow-Methods "POST, GET, OPTIONS"
# force apache to return 200 without executing my scripts
RewriteEngine On
RewriteCond %{REQUEST_METHOD} OPTIONS
RewriteRule .* / [R=200,L]
You may not need the latter part, depending on what happens when Apache executes your target script. Credit goes to the friendly ServerFault folk for the latter part.
This PHP at the top of the responding script seems to work. (With Firefox 3.6.11. I have not yet done a lot of testing.)
header('Access-Control-Allow-Origin: *');
header('Access-Control-Allow-Methods: POST, GET, OPTIONS');
header('Access-Control-Max-Age: 1000');
if(array_key_exists('HTTP_ACCESS_CONTROL_REQUEST_HEADERS', $_SERVER)) {
header('Access-Control-Allow-Headers: '
. $_SERVER['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']);
} else {
header('Access-Control-Allow-Headers: *');
}
if("OPTIONS" == $_SERVER['REQUEST_METHOD']) {
exit(0);
}
I had same problem with sending requests to google maps, and solution is quite simple with jQuery 1.5 - for dataType use dataType: "jsonp"
Culprit is preflight request using OPTIONS method
For HTTP request methods that can cause side-effects on user data (in particular, for HTTP methods other than GET, or for POST usage with certain MIME types), the specification mandates that browsers "preflight" the request, soliciting supported methods from the server with an HTTP OPTIONS request method, and then, upon "approval" from the server, sending the actual request with the actual HTTP request method.
Web specification refer to: https://developer.mozilla.org/en-US/docs/Web/HTTP/Access_control_CORS
I resolved the problem by adding following lines in Nginx conf.
location / {
if ($request_method = OPTIONS ) {
add_header Access-Control-Allow-Origin "*";
add_header Access-Control-Allow-Methods "POST, GET, PUT, UPDATE, DELETE, OPTIONS";
add_header Access-Control-Allow-Headers "Authorization";
add_header Access-Control-Allow-Credentials "true";
add_header Content-Length 0;
add_header Content-Type text/plain;
return 200;
}
location ~ ^/(xxxx)$ {
if ($request_method = OPTIONS) {
rewrite ^(.*)$ / last;
}
}
I was looking through source 1.3.2, when using JSONP, the request is made by building a SCRIPT element dynamically, which gets past the browsers Same-domain policy. Naturally, you can't make a POST request using a SCRIPT element, the browser would fetch the result using GET.
As you are requesting a JSONP call, the SCRIPT element is not generated, because it only does this when the Type of AJAX call is set to GET.
http://dev.jquery.com/ticket/4690
We had a problem like this with ASP.Net. Our IIS was returning an Internal Server Error when trying to execute a jQuery $.post to get some html content due to PageHandlerFactory was restricted to respond only GET,HEAD,POST,DEBUG Verbs. So you can change that restriction adding the verb "OPTIONS" to the list or selecting "All Verbs"
You can modify that in your IIS Manager, selecting your website, then selecting Handler Mappings, double click in your PageHandlerFactory for *.apx files as you need (We use Integrated application pool with framework 4.0). Click on Request Restrictions, then go to Verbs Tabn and apply your modification.
Now our $.post request is working as expected :)
Check if your form's action URL includes the www part of the domain, while the original page you have opened is viewed without www.
Typically done for Canonical Urls..
I struggled for hours before stumbling upon this article and found the hint of Cross Domain.
I seems that if o.url = 'index.php' and this file exists is ok and returning a success message in the console. It returns an error if I use url:http://www.google.com
If doing a post request why not using directly the $.post method:
$.post("test.php", { func: "getNameAndTime" },
function(data){
alert(data.name); // John
console.log(data.time); // 2pm
}, "json");
It is so much simpler.
I have posted a clear example of how to solve this if control the server code of the domain you are POSTing to. This answer is touched on in this thread, but this more clearly explains it IMO.
How do I send a cross-domain POST request via JavaScript?
Solution to this is:
use dataType: json
add &callback=? to your url
this worked on calling Facebook API and with Firefox. Firebug is using GET instead of OPTIONS with the above conditions (both of them).
Another possibility to circumvent the problem is to use a proxy script. That method is described for example here
Can you try this without
contentType:application/x-www-form-urlencoded
Try adding the option:
dataType: "json"
function test_success(page,name,id,divname,str)
{
var dropdownIndex = document.getElementById(name).selectedIndex;
var dropdownValue = document.getElementById(name)[dropdownIndex].value;
var params='&'+id+'='+dropdownValue+'&'+str;
//makerequest_sp(url, params, divid1);
$.ajax({
url: page,
type: "post",
data: params,
// callback handler that will be called on success
success: function(response, textStatus, jqXHR){
// log a message to the console
document.getElementById(divname).innerHTML = response;
var retname = 'n_district';
var dropdownIndex = document.getElementById(retname).selectedIndex;
var dropdownValue = document.getElementById(retname)[dropdownIndex].value;
if(dropdownValue >0)
{
//alert(dropdownValue);
document.getElementById('inputname').value = dropdownValue;
}
else
{
document.getElementById('inputname').value = "00";
}
return;
url2=page2;
var params2 = parrams2+'&';
makerequest_sp(url2, params2, divid2);
}
});
}
I had a similar problem with trying to use the Facebook API.
The only contentType which didn't send the Preflighted request seemed to be just text/plain... not the rest of the parameters mentioned at mozilla here
Why is this the only browser which does this?
Why doesn't Facebook know and accept the preflight request?
FYI: The aforementioned Moz doc suggests X-Lori headers should trigger a Preflighted request ... it doesn't.
You need to do some work on server side. I see you are using PHP on server side, but solution for .NET web application is here:
Cannot set content-type to 'application/json' in jQuery.ajax
Do the same in PHP script and it will work. Simply: At first request browser is asking server if is allowed to send such data with such type and second request is the proper/allowed.
Try to add the following:
dataType: "json",
ContentType: "application/json",
data: JSON.stringify({"method":"getStates", "program":"EXPLORE"}),
I used a proxy url to solve a similar problem when I want to post data to my apache solr hosted in another server. (This may not be the perfect answer but it solves my problem.)
Follow this URL: Using Mode-Rewrite for proxying, I add this line to my httpd.conf:
RewriteRule ^solr/(.*)$ http://ip:8983/solr$1 [P]
Therefore, I can just post data to /solr instead of posting data to http://ip:8983/solr/*. Then it will be posting data in the same origin.
I already have this code handling well my cors situation in php:
header( 'Access-Control-Allow-Origin: '.CMSConfig::ALLOW_DOMAIN );
header( 'Access-Control-Allow-Headers: '.CMSConfig::ALLOW_DOMAIN );
header( 'Access-Control-Allow-Credentials: true' );
And it was working fine locally and remotely, but not for uploads when remote.
Something happen with apache/php OR my code, I didn't bother to search it, when you request OPTIONS it returns my header with cors rules but with 302 result. Therefore my browser doesn't recognise as an acceptable situation.
What I did, based on #Mark McDonald answer, is just put this code after my header:
if( $_SERVER['REQUEST_METHOD'] === 'OPTIONS' )
{
header("HTTP/1.1 202 Accepted");
exit;
}
Now, when requesting OPTIONS it will just send the header and 202 result.
Please be advised:
JSONP supports only the GET request method.
*Send request by firefox:*
$.ajax({
type: 'POST',//<<===
contentType: 'application/json',
url: url,
dataType: "json"//<<=============
...
});
Above request send by OPTIONS(while ==>type: 'POST')!!!!
$.ajax({
type: 'POST',//<<===
contentType: 'application/json',
url: url,
dataType: "jsonp"//<<==============
...
});
But above request send by GET(while ==>type: 'POST')!!!!
When you are in "cross-domain communication" , pay attention and be careful.