How to send to Amazon's Alexa Event Gateway? - node.js

Question

I am trying to test sending an event to the Amazon's Event Gateway for my Alexa Smart Home skill using Postman but I keep receiving an 'invalid access token exception.' I have read the Amazon's documentation on this but apparently I am missing something.
When I enable my skill, my Smart Home Lambda receives the AcceptGrant.
{
"directive": {
"header": {
"namespace": "Alexa.Authorization",
"name": "AcceptGrant",
"messageId": "b2862179-bc56-4bb2-ac05-ce55c7a3e977",
"payloadVersion": "3"
},
"payload": {
"grant": {
"type": "OAuth2.AuthorizationCode",
"code": "ANSVjPzpTDBsdfoRSyrs"
},
"grantee": {
"type": "BearerToken",
"token": "Atza|IwEB..."
}
}
}
}
My lambda sends a POST to 'https://api.amazon.com/auth/o2/token' to receive the Access and Refresh tokens. It then stores those tokens. Next, my Lamdba responds with the following:
{
"event": {
"header": {
"namespace": "Alexa.Authorization",
"name": "AcceptGrant.Response",
"messageId": "b2862179-bc56-4bb2-ac05-ce55c7a3e977",
"payloadVersion": "3"
},
"payload": {}
}
}
I then get a message web page that I have successfully linked my skill - all is good.
Next, I try to send an event to Amazon's Alexa event gateway using the Postman app. I put the Access token (I also tried the Refresh token) in the header as a 'BearerToken' type and the in the 'scope' of the 'endpoint' object.
POST https://api.amazonalexa.com/v3/events?Content-Type=application/json&charset=UTF-8
with a header that specifies a Bearer Token (Access token received earlier) and a body that contains the following:
{
"event": {
"header": {
"messageId": "abc-123-def-456",
"namespace": "Alexa",
"name": "ChangeReport",
"payloadVersion": "3"
},
"endpoint": {
"scope": {
"type": "BearerToken",
"token": "<access token>"
},
"endpointId": "MySmartSwitch-001"
},
"payload": {
"change": {
"cause": {
"type": "RULE_TRIGGER"
},
"properties": [
{
"namespace": "Alexa.ModeController",
"name": "mode",
"value": "Backup",
"timeOfSample": "2020-01-02T09:30:00ZZ",
"uncertaintyInMilliseconds": 50
}
]
}
}
},
"context": {
"properties": [
{
"namespace": "Alexa.PowerController",
"name": "powerState",
"value": "ON",
"timeOfSample": "2020-01-02T09:30:00Z",
"uncertaintyInMilliseconds": 60000
},
{
"namespace": "Alexa.EndpointHealth",
"name": "connectivity",
"value": {
"value": "OK"
},
"timeOfSample": "2020-01-02T09:30:00Z",
"uncertaintyInMilliseconds": 0
}
]
}
}
The response received is '401 Unauthorized'
{
"header": {
"namespace": "System",
"name": "Exception",
"messageId": "95bd23c3-76e6-472b-9c6d-74d436e1eb61"
},
"payload": {
"code": "INVALID_ACCESS_TOKEN_EXCEPTION",
"description": "Access token is not valid."
}
}

Answer 1

I figured out the issue. I was mistakenly sending parameters: Content-Type=application/json and charset=UTF-8 as well including them in the header - my bad. You just need to include them in the header.