WebSocket API: How to use FIDs rather than field names for posting

Hi,

we were asked by Refinitiv to migrate our MLIP/MFOT-based application to RCC / WebSocket API.

Question now: How can we contribute to RICs and use FIDs rather than field names for the post message?

All code examples I have seen so far, use field names and not FIDs in the JSON message like this:

"Type":"Post",
"PostID":"1",
"Domain":"MarketPrice",
...

"Message":{
  "ID":0,
  "Type":"Update",
  "Domain":"MarketPrice",
  "Fields":{
    "BID": 45.55,
    "BIDSIZE": 18,
    "ASK": 45.57,
    "ASKSIZE": 19
  }
}
...

The reason for this question is, that all our setup for contributing pages and RIC data is based on FIDs, and not field names, as MFOT did only accept FIDs.

Kind regards,

Wolfgang Hege