Error: No 'Access-Control-Allow-Origin' header in a Python web server

Question

I've a problem with a python web server based on HTTPServer:

INTRODUCTION: I've a system of cameras: 2 in each computer. Each computer has his python web server which manage the cameras settings. The camera settings are stored in a xml file. Then I've another computer with a software (in python) which manage the data from the cameras. Also this software has a settings file in xml and a web server in python

PROBLEM: I did an interface in html/jquery which send requests to the servers. The problem is when I send an Ajax request to the server situated in the "cameras computer" for the xml file from a page situated in another server.

This is the AJAX Request:

$.ajax({
        type: "GET",
        url: "http://"+ipCompleto+":8081/"+$(this).attr("port")+"/default.xml",
        dataType: "xml",
        success: function(xml){

            bordoBlob = $(xml).find('dimBordoBlob').text();
            blobSize = $(xml).find('blobSize').text();
            hMin = $(xml).find('intval1').text();
            hMax = $(xml).find('intval2').text();
            $("#inputHMax").val(hMax);
            $("#titoloHMax").text(hMax);
            $("#inputHMin").val(hMin);
            $("#titoloHMin").text(hMin);
            $("#minBlobSizeValue").val(blobSize);
            $("#minBlobSizeTitle").text(blobSize);
            $("#blobBorderSizeValue").val(blobSize);
            $("#blobBorderSizeTitle").text(blobSize);   
        },
        error: function() {
            alert("An error occurred while processing XML file.");
        }       
    });

This is the server:

#!/usr/bin/env python
from http.server import BaseHTTPRequestHandler, HTTPServer
from xml.dom import minidom
import os
import time
from stat import *
class MyHandler(BaseHTTPRequestHandler):
    def do_POST(self):
        self.data_string = self.rfile.read(int(self.headers['Content-Length']))
        self.send_response(200)
        self.end_headers()
        valore = str(self.data_string)[2:-1]
        response = ["",""]
        response[0],response[1] = processData(valore)
        if response[0] == 1:
            sep = ""
            message = ""
            for res in response[1]:
                message += res
            response = sep.join(message)
            self.wfile.write(bytes(message, "utf-8"))

    def do_GET(self):
        # Send response status code
        self.send_response(200)
        self.send_header('Cache-Control', 'no-store, no-cache, must-revalidate, post-check=0, pre-check=0')
        # Send headers
        if self.path.endswith("html"):
            self.send_header('Content-type', 'text/html')
            self.end_headers()
        elif self.path.endswith("css"):
            self.send_header('Content-type', 'text/css')
            self.end_headers()
        elif self.path.endswith("xml"):
            self.send_header('Content-type', 'text/xml')
            self.end_headers()
        elif self.path.endswith("js"):
            self.send_header('Content-type', 'application/javascript')
            self.end_headers()
        if not self.path.endswith("jpeg") and not self.path.endswith("jpg") and not self.path.endswith("png") and not self.path.endswith("gif"):
            with open(self.path[1:], 'r') as myfile:
                data = myfile.read()
            # Write content as utf-8 data
            self.wfile.write(bytes(data, "utf8"))
        if self.path.endswith("jpeg"):
            f = open(self.path[1:], 'rb')
            self.send_response(200)
            self.send_header('Content-type', 'image/jpeg')
            self.send_header('Cache-Control', 'no-store')
            self.end_headers()
            self.wfile.write(f.read())
            f.close()
        elif self.path.endswith("png"):
            f = open(self.path[1:], 'rb')
            self.send_response(200)
            self.send_header('Content-type', 'image/png')
            self.end_headers()
            self.wfile.write(f.read())
            f.close()
        elif self.path.endswith("gif"):
            f = open(self.path[1:], 'rb')
            self.send_response(200)
            self.send_header('Content-type', 'image/gif')
            self.end_headers()
            self.wfile.write(f.read())
            f.close()
        elif self.path.endswith("jpg"):
            f = open(self.path[1:], 'rb')
            self.send_response(200)
            self.send_header('Content-type', 'image/jpeg')
            self.end_headers()
            self.wfile.write(f.read())
            f.close()
        return

def run():
    print('starting server...')

    # Server settings
    # Choose port 8080, for port 80, which is normally used for a http server, you need root access
    server_address = ('192.168.2.245', 8081)
    httpd = HTTPServer(server_address, MyHandler)
    print('running server...')
    httpd.serve_forever()


def processData(data):
    XMLlist = []
    data = data.split(":")
    field = data[0].split(">")
    print(data,field,data[2])
    try:
        exists = field[2]
    except:
        exists = False
    if data[0] == "XMLlist":
        path = os.path.realpath(__file__)
        path = os.path.dirname(path)
        path = path+"/"+data[2]
        for filename in os.listdir(path):
            if filename.endswith('.xml'):
                XMLlist.append(filename[:-3])
        return 1,XMLlist
    elif exists != False:
        file = open(data[2]+data[3], 'r')
        tree = minidom.parse(file)
        camera = tree.getElementsByTagName(field[0])
        for element in camera:
            if element.getAttribute('id') == str(field[1]):
                print(data[1], field[0], field[1], field[2])
                element.getElementsByTagName(field[2])[0].childNodes[0].replaceWholeText(data[1])
        file = open(data[2]+data[3], 'w')
        tree.writexml(file)
        file.close()
        return 0, 0
    else:
        print(data)
        file = open(data[2]+data[3], 'r')
        tree = minidom.parse(file)
        tree.getElementsByTagName(data[0])[0].childNodes[0].replaceWholeText(data[1])
        file = open(data[2]+data[3], 'w')
        tree.writexml(file)
        file.close()
        return 0, 1
run()

Thank you for the answers and sorry for my bad english!

This worked for me: gist.github.com/enjalot/2904124

robocat
– robocat

2019-03-13 02:46:52 +00:00
Commented Mar 13, 2019 at 2:46 — robocat
– robocat, Commented Mar 13, 2019 at 2:46

Community · Accepted Answer · 2017-05-23 12:17:44Z

2

The Access-Control-Allow-Origin response header indicates whether the response can be shared with resources with the given origin.

You need to add this header to your response :

Access-Control-Allow-Origin: *

Unfortunately, SimpleHTTPServer is really that simple that it does not allow any customization, especially not of the headers it sends. You can however create a simple HTTP server yourself, using most of SimpleHTTPServerRequestHandler, and just add that desired header. or subclass SimpleHTTPServer.SimpleHTTPRequestHandler and changeing the behavior of end_headers()

import SimpleHTTPServer

class MyHTTPRequestHandler(SimpleHTTPServer.SimpleHTTPRequestHandler):
    def end_headers(self):
        self.send_my_headers()

        SimpleHTTPServer.SimpleHTTPRequestHandler.end_headers(self)

    def send_my_headers(self):
        self.send_header("Access-Control-Allow-Origin", "*")

if __name__ == '__main__':
    SimpleHTTPServer.test(HandlerClass=MyHTTPRequestHandler)

Thank this answer for the code & This guy answer has all what you need to understand cros

edited May 23, 2017 at 12:17

CommunityBot

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answered Apr 10, 2017 at 8:50

user3176898

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1 Comment

G. Threepwood Over a year ago

thank you very much. I'll try to follow the answers! I'll let you know...

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