twilio App to App calling is not working

Question

I have setup TwiMl on eroku in Python. When I call user A from user B, user A didn't get call and VOIP also, while user B is got bot message like "thanks for calling".

When I try to placeCall to user B from PostMan, user B gets call and also got bot message like "thanks for calling".

PostMan URL : https://myapp.herokuapp.com/placeCall

My requirement is when I call user A from application user B will get call and both can able to communicate.

Requirement

Flask==0.10.1
Jinja2==2.7.3
MarkupSafe==0.23
Werkzeug==0.9.6
httplib2==0.9
itsdangerous==0.24
six==1.*
twilio
wsgiref==0.1.2

Here is my Python TwiMl Code.

import os
from flask import Flask, request
from twilio.jwt.access_token import AccessToken
from twilio.jwt.access_token.grants import VoiceGrant
from twilio.rest import Client
import twilio.twiml

ACCOUNT_SID = 'ACxxxxxxxx'
API_KEY = 'SKxxxxxxxx'
API_KEY_SECRET = 'TSxxxxxxxx'
PUSH_CREDENTIAL_SID = 'CRxxxxxxxx'
APP_SID = 'APxxxxxxxx'


app = Flask(__name__)

@app.route('/test', methods=['GET', 'POST'])
def test():

    req_json = request.get_json(force=True)
    UserName = req_json['username']
    Password = req_json['password']
    return str(UserName)

@app.route('/accessToken')
def token():

    IDENTITY = request.args.get('identity')
    account_sid = os.environ.get("ACCOUNT_SID", ACCOUNT_SID)
    api_key = os.environ.get("API_KEY", API_KEY)
    api_key_secret = os.environ.get("API_KEY_SECRET", API_KEY_SECRET)
    push_credential_sid = os.environ.get("PUSH_CREDENTIAL_SID", PUSH_CREDENTIAL_SID)
    app_sid = os.environ.get("APP_SID", APP_SID)

    grant = VoiceGrant(push_credential_sid=push_credential_sid,outgoing_application_sid=app_sid)

    token = AccessToken(account_sid, api_key, api_key_secret, IDENTITY)
    token.add_grant(grant)

    return str(token)

@app.route('/outgoing', methods=['GET', 'POST'])
def outgoing():

    req_json = request.get_json(force=True)
    CALLER_ID = req_json['callerid']
    resp = twilio.twiml.VoiceResponse()
    dial = Dial()
    dial.client(CALLER_ID)
    resp.append(dial)
    #resp.say("Congratulations! You have made your first oubound call! Good bye.")
    #resp.say("Thanks for Calling.",voice='woman',)
    return str(resp)

@app.route('/incoming', methods=['GET', 'POST'])
def incoming():
    resp = twilio.twiml.VoiceResponse()
    #resp.say("Congratulations! You have received your first inbound call! Good bye.")
    #resp.say("Thanks for Calling.",voice='woman',)
    return str(resp)

@app.route('/placeCall', methods=['GET', 'POST'])
def placeCall():

    req_json = request.get_json(force=True)
    IDENTITY = req_json['identity']
    CALLER_ID = req_json['callerid']
    account_sid = os.environ.get("ACCOUNT_SID", ACCOUNT_SID)
    api_key = os.environ.get("API_KEY", API_KEY)
    api_key_secret = os.environ.get("API_KEY_SECRET", API_KEY_SECRET)
    client = Client(api_key, api_key_secret, account_sid)
    call = client.calls.create(url=request.url_root + 'incoming', to='client:' + CALLER_ID, from_='client:' + IDENTITY)
    return str(call.sid)

@app.route('/', methods=['GET', 'POST'])
def welcome():
    resp = twilio.twiml.VoiceResponse()
    resp.say("Welcome")
    return str(resp)

if __name__ == "__main__":
    port = int(os.environ.get("PORT", 5000))
    app.run(host='0.0.0.0', port=port, debug=True)

Error Logs

TwiML setting on twilio dashboard

Request URL : https://myapp.herokuapp.com/outgoing

Please let me know is there anything that I missed to configure or something that I have done wrong.

Tutorial that I followed to configure TwiML is Here

Answer 1

Twilio developer evangelist here.

I'm not sure whether you're building an iOS or Android app, but the idea is the same. When you place a call, like in the example here from the iOS quickstart in Swift, using code like this:

TwilioVoice.sharedInstance().call(accessToken, params: [:], delegate: self)

you should send some parameters with that call, for example the client identity that you are calling. e.g.

TwilioVoice.sharedInstance().call(accessToken, params: ["To": "ClientIdentity"], delegate: self)

Then, Twilio will call the URL you set in your TwiML application. In the quickstart the url should be /outgoing and in the quickstart application you get an example voice message. To make the call to another application you need to return a different response from /outgoing. In this case, you need to use <Dial> with a nested <Client> using the To parameter passed when making the call.

In Python/Flask this would look like:

@app.route('/outgoing', methods=['GET', 'POST'])
def outgoing():
    resp = twilio.twiml.Response()
    dial = Dial()
    dial.client(request.form['To'])
    response.append(dial)
    return str(resp)

I notice that in the comments on the question you changed the TwiML App URL to /placeCall. Make sure you change that back to /outgoing.

Let me know if this helps at all.