How to read, process variable POST, Python HTTP Server

Question

Server code

#!/usr/bin/env python
import BaseHTTPServer
from BaseHTTPServer import BaseHTTPRequestHandler
import SocketServer
import urlparse
import cgitb
import cgi
from cgi import parse_header, parse_multipart


class S(BaseHTTPRequestHandler):
 def _set_headers(self):
  self.send_response(200)
  self.send_header('Content-type', 'text/html')
  self.end_headers()

 def do_GET(self):
   self._set_headers()
   self.wfile.write("<html><body><h1>hi!</h1></body></html>")

 def do_HEAD(self):
   self._set_headers()

 def do_POST(self):
  ctype, pdict = cgi.parse_header(self.headers.getheader('content-type'))
  if ctype == 'multipart/form-data':
   postvars = cgi.parse_multipart(self.rfile, pdict)
  elif ctype == 'application/x-www-form-urlencoded':
   length = int(self.headers.getheader('content-length'))
   postvars = cgi.parse_qs(self.rfile.read(length), keep_blank_values=1)
  else:
   postvars = {}

def run(server_class=BaseHTTPServer.HTTPServer, handler_class=S, port=80):
 server_address = ('', port)
 httpd = server_class(server_address, handler_class)
 print 'Starting httpd...'
 httpd.serve_forever()

if __name__ == "__main__":

        run()

Clinet

Client send POST request over program Postman.

GET works.

Post is does not work . This is Error on server when I send request

http://192.168.2.108?var1=value

ERROR ON SERVER

Exception happened during processing of request from ('192.168.2.107', 49629) Traceback (most recent call last): File "/usr/lib/python2.7/SocketServer.py", line 295, in _handle_request_noblock self.process_request(request, client_address) File "/usr/lib/python2.7/SocketServer.py", line 321, in process_request self.finish_request(request, client_address) File "/usr/lib/python2.7/SocketServer.py", line 334, in finish_request self.RequestHandlerClass(request, client_address, self) File "/usr/lib/python2.7/SocketServer.py", line 655, in init self.handle() File "/usr/lib/python2.7/BaseHTTPServer.py", line 340, in handle self.handle_one_request() File "/usr/lib/python2.7/BaseHTTPServer.py", line 328, in handle_one_request method() File "server.py", line 37, in do_POST ctype, pdict = cgi.parse_header(self.headers.getheader('content-type')) File "/usr/lib/python2.7/cgi.py", line 309, in parse_header parts = _parseparam(';' + line) TypeError: cannot concatenate 'str' and 'NoneType' objects

Why did you make the exception text unreadable again? Instead of making it hard to read the exception you could spend your time printing the content-type to see if its really in the header or returning None. If parse_header is erroring because of None, there is a significant chance that you are passing in a None. — tdelaney
Thank you tdelaney. Problem was in Postman. probably I set wrong values. Post works on Android studio — user7432329

Cans Cans · Accepted Answer · 2017-02-18T17:53:31

Maybe because the request sent by your client does not include the content-type header.

You did not say how you are connecting to the server.

curl -X POST http://localhost:8880/?var1=value

Will fail as shown above. While:

 curl -X POST http://localhost:8880/?var1=value -H 'Content-type: application/x-www-form-urlencoded'

Will fail also, but a bit further along the way: you also need a Content-length header. What you need is to check the values returned to you by the class methods instead of trusting everything will happen as you wish it will:

def do_POST(self):
    content_type = self.headers.getheader('content-type')
    if content_type is None:
        raise ... # 400 Invalid Request

    # otherwise go on.

How to read, process variable POST, Python HTTP Server

1 Answers