adding POST to the SimpleHTTPServer as proxy

Question

UPDATED I've made simple proxy based on SimpleHTTPServer but i've got problem with POST method when someone is requesting with POST method it show Error so i've made do_POST() function,but when i requesting with POST (works fine with most site except vbulletin script !) i just get page says:The connection was reset

so now the problem is when i try to login at vbulletin site it said The connection was reset i have no idea why !

class Proxy(SimpleHTTPServer.SimpleHTTPRequestHandler):
    def do_GET(self):
      print self.address_string()
      print "User ip:",self.client_address[0]
      print self.date_time_string()#return time
      print self.path
      print self.headers
      self.copyfile(urllib.urlopen(self.path), self.wfile)
      print "--------------------------------------------\n"
    #this is the function where is the problem 
    def do_POST(self):
      print "=====================\n"
      print self.raw_requestline
      print self.headers.getheaders("Content-Length")
      length = int(self.headers.getheaders("Content-Length")[0])
      post_data = urlparse.parse_qs(self.rfile.read(length))
      self.copyfile(urllib.urlopen(self.path,urllib.urlencode(post_data)),self.wfile)
      print "=====================\n"

hopefully i can get hint about it