sim800 at command post data to server - http

Question

I'm stumped with sending data to a remote server , I'm able to send a post request but not sure how to add data which is then received by the server.
I've went through the datasheet http://www.jarzebski.pl/datasheets/SIM900_https-121018-1.00.pdf
tried
# usual at+sapbr=1,1 set up
+HTTPINIT
+HTTPPARA = “CID”,1
+HTTPPARA="URL","IP-ADDRESS:PORT"
+httpdata=100,10000
# Where do I add the post data ?
+httpaction=1
which sends the http post request. But how do I add data - I've tried adding it to the url ?key=val but no joy - any help here will be appreciated

Answer 1

httpdata=100,10000 means that SIM800 should expect 100 bytes within 10 seconds.
This is how I accomplished this using the HTTP client:
AT+HTTPINIT
AT+HTTPPARA="CID",1
AT+HTTPPARA="URL","http://url.com/endPoint"
AT+HTTPPARA="CONTENT","application/json"
AT+HTTPDATA=40,10000
At this point, the SIM800 should respond with "DOWNLOAD". Which means it's expecting your data. Send in your data; in my case:
{"location_id": 238, "fill_percent": 90}
Wait 10 seconds to send the rest of the commands. Then:
AT+HTTPACTION=1
AT+HTTPREAD
AT+HTTPTERM
That did it for me. Hope it helps.
This is where I got the information from: http://www.raviyp.com/embedded/194-sim900-gprs-http-at-commands
In the backend, using Python Flask, this is the code I used
#app.route('/reportTrashLevel', methods=['POST'])
def report_trash_level():
data = request.get_json()
database.insert_trash_level(data)
return Response(status=200)

Answer 2

I managed to get it to do what I need, this code-snippet will likely help others
AT+CGATT=1 # enter GPRS configuration mode
AT+CIPMUX=0 # Disable multi IP connection mode. Single IP cnxn only
AT+CSTT="APN","USER","PASS"
AT+CIICR # bring up wireless connection with GPRS and CSD
AT+CIFSR # ip up - gprs working
AT+CIPSHUT # Exit GPRS configuration mode
# Now do a post request to remote server api in json format.
# Change IP_ADDR|DOMAIN for the IP or domain name of your server.
# Change 2000 to its port
AT+CIPSTART="TCP","IP_ADDR|DOMAIN","2000"
AT+CIPSEND=119 # Num of char in tcp/ip data, \r & \n count as 1 char
POST /post HTTP/1.1
Host: **.**.***.***
Content-Type: application/json
Content-Length:23
{"postkey":"postvalue"}
Hope this helps the next person stuck on it.