Http post from device has no content

Hi all,
could you please help me with a problem posting json data to a service using ionic 2?

when i make a post with json-data on a mac (ionic serve), the call arrives at the service (windows machine), json data is included (see dump 1).
When i do the same post on an ios device (iphone), the call also arrives at the service (including preflight etc., all ok), but the json data is not included (->content lengh is zero, see dump 2)

I have no idea what could be the reason for this (CORS should all be ok as I can see the OPTIONS call, the ack back to the app and then the post… The post is working on android devices as well as in ionic serve (app and service on different machines) (the only difference I realized is the referer, but both are remote machines…)

dump 1 (ionic serve on mac) (this has the post data included)
Hypertext Transfer Protocol
POST /FactWorkProjectPlanRestSvc/testCall HTTP/1.1\r\n
[Expert Info (Chat/Sequence): POST /FactWorkProjectPlanRestSvc/testCall HTTP/1.1\r\n]
[POST /FactWorkProjectPlanRestSvc/testCall HTTP/1.1\r\n]
[Severity level: Chat]
[Group: Sequence]
Request Method: POST
Request URI: /FactWorkProjectPlanRestSvc/testCall
Request Version: HTTP/1.1
Host: 10.80.10.94:8732\r\n
Access-Control-Allow-Origin: *\r\n
Accept: /\r\n
Access-Control-Allow-Methods: GET,PUT,POST,DELETE\r\n
Access-Control-Allow-Headers: Origin,X-Requested-With,Content-Type,Accept\r\n
Accept-Language: de-de\r\n
Accept-Encoding: gzip, deflate\r\n
Content-Type: application/json\r\n
Origin: http://localhost:8100\r\n
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_3) AppleWebKit/602.4.8 (KHTML, like Gecko) Version/10.0.3 Safari/602.4.8\r\n
Referer: http://localhost:8100/\r\n
Content-Length: 120\r\n
[Content length: 120]
Connection: keep-alive\r\n
\r\n
[Full request URI: http://10.80.10.94:8732/FactWorkProjectPlanRestSvc/testCall]
[HTTP request 2/2]
[Prev request in frame: 94]
File Data: 120 bytes
JavaScript Object Notation: application/json
Object
Member Key: Username
String value: xxx
Key: Username

dump 2 (no content - iphone)
Hypertext Transfer Protocol
POST /FactWorkProjectPlanRestSvc/testCall HTTP/1.1\r\n
[Expert Info (Chat/Sequence): POST /FactWorkProjectPlanRestSvc/testCall HTTP/1.1\r\n]
[POST /FactWorkProjectPlanRestSvc/testCall HTTP/1.1\r\n]
[Severity level: Chat]
[Group: Sequence]
Request Method: POST
Request URI: /FactWorkProjectPlanRestSvc/testCall
Request Version: HTTP/1.1
Host: nbchriswe:8732\r\n
Access-Control-Allow-Origin: *\r\n
Accept: /\r\n
Access-Control-Allow-Methods: GET,PUT,POST,DELETE\r\n
Access-Control-Allow-Headers: Origin,X-Requested-With,Content-Type,Accept\r\n
Accept-Language: de-de\r\n
Accept-Encoding: gzip, deflate\r\n
Content-Type: application/json\r\n
Origin: http://ionic.local\r\n
User-Agent: Mozilla/5.0 (iPhone; CPU iPhone OS 10_2_1 like Mac OS X) AppleWebKit/602.4.6 (KHTML, like Gecko) Mobile/14D27 (5198883568)\r\n
Referer: http://ionic.local/var/containers/Bundle/Application/555EC584-2A14-4F3F-8746-1255F3525A8C/FactWork.ProjektPlan.app/www/index.html\r\n
Content-Length: 0\r\n
[Content length: 0]
Connection: keep-alive\r\n
\r\n
[Full request URI: http://nbchriswe:8732/FactWorkProjectPlanRestSvc/testCall]
[HTTP request 2/2]
[Prev request in frame: 20404]
[Response in frame: 21295]

System Info:
Cordova CLI: 6.5.0
Ionic Framework Version: 2.0.1
Ionic CLI Version: 2.1.17
Ionic App Lib Version: 2.1.7
Ionic App Scripts Version: 1.0.0
ios-deploy version: 1.9.1
ios-sim version: 5.0.13
OS: macOS Sierra
Node Version: v7.2.1
Xcode version: Xcode 8.2.1 Build version 8C1002

Thanks in advance,
Chris

Switch to HTTPS.

That did it, thank you!