Question

Getting Response is null error while receiving HTTP response.
I am developing an sample small HTTP server in C using row sockets.

There are actually 2 servers in my application one is standard Apache server which I am using for serving HTML pages and my small server will respond to only XMLHttpRequest sent from the Javascript within the HTML pages.

I am sending request from JavaScript as follows:

var sendReq = new XMLHttpRequest();
endReq.open("POST", "http://localhost:10000/", true);
sendReq.setRequestHeader('Content-Type','application/x-www-form-urlencoded');
sendReq.onreadystatechange = handleResult;
var param = "REQUEST_TYPE=2002&userName=" + userName.value;
param += "&password=" + password.value;
sendReq.send(param);

When I send this request I receive following Request in my server code:

OPTIONS / HTTP/1.1
Host: localhost:10000
User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.3) Gecko/20100423 Ubuntu/10.04 (lucid) Firefox/3.6.3
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: 115
Connection: keep-alive
Origin: http://localhost:7777
Access-Control-Request-Method: POST

I have replied to this Request as follows using socket write function:

HTTP/1.1 200 OK\n
Access-Control-Allow-Origin: *\n
Server: PSL/1.0 (Unix) (Ubuntu/Linux)\n
Access-Control-Allow-Methods: POST, GET, OPTIONS\n
Accept-Ranges: bytes\n
Content-Length: 438\nConnection: close\n
Content-Type: text/html; charset=UTF-8\n\n

I don`t know What should be the HTTP actual response to be sent on request of OPTIONS.
After this I get my Actual POST request that I have sent from JavaScript and then I respond back with

HTTP/1.1 200 OK\n\n

And then at the browser end get error Response is null.

So how to send headers/data as HTTP Response using row sockets in ‘C’ and how to respond to OPTIONS request. Can someone explain me by giving some example?

Answer 1

This problem had occured as after processing the OPTIONS request by our server, any subsequent requests made, for some reason, were required to be responded back with “Access-Control-Allow-Origin: *” along with other normal headers and response body.

After providing this line in our responses, I always got the desired responseText/responseXML in my javascript.