client.py

from twisted.internet import reactor
from twisted.python import log
from twisted.internet.protocol import Protocol
from twisted.internet.defer import Deferred

from StringIO import StringIO
from twisted.web.http_headers import Headers
from twisted.web.client import Agent, FileBodyProducer

import json
class BeginningPrinter(Protocol):
    """Concatenates and returns (as a deferred) a request response"""
    def __init__(self, finished):
        self.finished = finished
        self.remaining = 1024 * 10
        self.data = ''
    def dataReceived(self, bytes):
        if self.remaining:
            display = bytes[:self.remaining]
            self.data += display
            self.remaining -= len(display)

    def connectionLost(self, reason):
        self.finished.callback(self.data)


def send_query(query, host_port):
        """Send a HTTP POST-query to a given host (possibly on a specific port)"""
        indexquery_string = json.dumps(query)
      
        QUERY = """
POST / HTTP/1.1
User-Agent: Artikkelgjennfinning
Content-Type: application/json
Content-Length: {LEN}

{JSON_STRING}""".strip().replace('\n', '\r\n').format(LEN=len(indexquery_string), 
                                                      JSON_STRING=indexquery_string)
        agent = Agent(reactor)
        d = agent.request('POST', host_port, None,FileBodyProducer(StringIO(indexquery_string)))
        def cbRequest(response):
            finished = Deferred()
            response.deliverBody(BeginningPrinter(finished))
            return finished
        d.addCallback(cbRequest)

        #Returns a deferred for the request response
        return d