Python proxy server for forwarding request.

server.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

"""Usage:
- Windows OS:
$ set FORWARD_HOST=http://example.com[:port]
$ python server.py
- Unix based OS (Ubuntu, MacOS .etc):
$ export FORWARD_HOST=http://example.com[:port]
$ python server.py"""

import os
import requests
from flask import Flask, abort, request, Response


FORWARD_HOST_KEY = 'FORWARD_HOST'
FORWARD_EXCLUDED_HEADER_KEYS = ['Host']
RESPONSE_EXCLUDED_HEADER_KEYS = [
        'content-encoding', 'content-length', 'transfer-encoding', 'connection']

app = Flask(__name__)

@app.route('/', methods=['GET', 'POST'])
def index():
    return doForward(request)

def getForwardHost():
    if FORWARD_HOST_KEY in os.environ:
        return os.environ[FORWARD_HOST_KEY]
    else:
        return None

def setForwardHost(host_url):
    os.environ[FORWARD_HOST_KEY] = host_url

def doForward(request):
    forward_host = getForwardHost()
    if forward_host is None:
        # Build forward host not found
        abort(404)
    else:
        # Build forward request
        forward_url = request.url.replace(request.host_url, forward_host)
        forward_headers = {key: value for (key, value) in
                request.headers if key.lower() not in FORWARD_EXCLUDED_HEADER_KEYS}
        receive = requests.request(method=request.method, url=forward_url, data=request.get_data(),
                headers=forward_headers, cookies=request.cookies, allow_redirects=False)

        # Build forwarded response
        response_headers = [(key, value) for (key, value) in
                receive.raw.headers.items() if key.lower() not in RESPONSE_EXCLUDED_HEADER_KEYS]
        return Response(receive.content, receive.status_code, response_headers)


if __name__ == '__main__':
    app.run(host='0.0.0.0', port=9119)