Ajax cross-Domain access error 501

Reference Documentation:

http://www.foreverpx.cn/2016/06/22/cross_content_type/

Problem:

Run the following code to make an error 501

$.ajax ({
            type: "POST",
        URL: "http://192.168.1.202/sensordata.php",

        contentType: ' Application/json; Charset=utf-8 ',
        data:JSON.stringify (ajaxpostdata),
        dataType: ' JSON ',
        success:function (data) {
            // On Ajax success does this
            console.info ("success.");
            if (data["status" = = = "OK") {
                alert ("The Settings is OK.") The Machine is rebooting. ");
            }
        ,
        error:function (XHR, ajaxoptions, thrownerror) {
            //on error do This
            console.info ("error.");
            if (Xhr.status =) {

                alert (ajaxoptions);
            }
            else {
                alert (xhr.status);
                alert (thrownerror);
            }
        }
    );

Workaround:

Remove ContentType: ' Application/json; Charset=utf-8 '

Reason:

4.1 In the Cross-domain, in addition to ContentType for application/x-www-form-urlencoded, Multipart/form-data or text/plain outside, Triggers a request that the browser first sends the method to options.

4.2 For example, your original request was a method method post, and if the Allow attribute in the header returned by the first request does not have a post method,

4.3 So the second request is not sent, the browser console will be an error, telling you that the POST method is not supported by the server.