These two files demonstrate how to send SMSes using AfricasTalking API (https://africastalking.com/) in an asynchronous way.

httpreq.py

#!/usr/bin/python2.7

import urllib
from twisted.internet import protocol
from twisted.internet import defer
from twisted.web.http_headers import Headers
from twisted.internet import reactor
from twisted.web.client import Agent
from twisted.web.iweb import IBodyProducer
from zope.interface import implements
from twisted.internet.defer import succeed


class StringProducer(object):
    implements(IBodyProducer)

    def __init__(self, body):
        self.body = body
        self.length = len(body)

    def startProducing(self, consumer):
        consumer.write(self.body)
        return succeed(None)

    def pauseProducing(self):
        pass

    def stopProducing(self):
        pass


class SimpleReceiver(protocol.Protocol):
    def __init__(self, d):
        self.buf = ''
        self.d = d

    def dataReceived(self, data):
        self.buf += data

    def connectionLost(self, reason):
        self.d.callback(self.buf)


def http_request(url, values=None, method='POST', headers=None, pool=None):
    from twisted.web import client
    client._HTTP11ClientFactory.noisy = False

    agent = Agent(reactor, pool=pool)
    data = urllib.urlencode(values) if values else None
    d = agent.request(
        method, url, Headers(headers) if headers else {},
        StringProducer(data) if data else None
    )

    def handle_response(response):
        if response.code == 204:
            d = defer.succeed('')
        else:
            d = defer.Deferred()
            response.deliverBody(SimpleReceiver(d))
        return d

    d.addCallback(handle_response)
    return d

tx-aft.py

#!/usr/bin/python2.7

import json

from httpreq import http_request
from twisted.internet import defer, reactor
from twisted.web.client import HTTPConnectionPool

pool = HTTPConnectionPool(reactor)
SEMA = None


def get_semaphore():
    """Limit number of concurrent operarions."""
    global SEMA
    if SEMA is None:
        SEMA = defer.DeferredSemaphore(150)
    return SEMA


sem = get_semaphore()


class Gateway:
    """Send message to AfricasTalking API asynchronously."""

    def __init__(self, uname, key):
        self.username = uname
        self.key = key
        self.url = "http://api.africastalking.com/version1/messaging"
        self.headers = {
            'Accept': ['application/json'], 'apikey': [key],
            'Content-Type': ['application/x-www-form-urlencoded'],
        }
        self.HTTP_RESPONSE_OK = 201
        self.debug = True

    def send_message(self, to, message, sid=None, sms_mode=1,
                     enqueue=0, keyword=None, link_id=None,
                     retry_hrs=None):
        payload = {
            'username': self.username, 'to': to,
            'message': message, 'bulkSMSMode': sms_mode}
        if sid is not None:
            payload["from"] = sid
        if enqueue > 0:
            payload["enqueue"] = enqueue
        if keyword is not None:
            payload["keyword"] = keyword
        if link_id is not None:
            payload["linkId"] = link_id

        if retry_hrs is not None:
            payload["retryDurationInHours"] = retry_hrs

        d = sem.run(
            http_request, self.url, payload, 'POST', self.headers, pool)
        d.addCallback(self._req_success)
        d.addErrback(self._req_failure)
    return d

    def _req_success(self, response):
        if self.debug:
            print "API: %s" % (response,)
        return json.loads(response)

    def _req_failure(self, error):
        if self.debug:
            print "Error on gateway: %s" % (error,)
        return 'Error on API'


def main():
    """Main method."""
    gw = Gateway('username', 'key')
    d = gw.send_message('0727372285', 'hello world')
    d.addCallback(send_success)
    d.addErrback(send_failed)
    return d


def send_success(result):
    print "Message sent successfully.\n Response: %s" % (result,)
    return


def send_failed(error):
    print "Error sending message: %s" % (error,)
    return


if __name__ == '__main__':
    main()