Send JSON via HTTPSOCKET POST?

When I have a JSON in a String.

How would I send it correct with HTTPSocket and POST with Xojo?

DIM Test_String As String
Test_String = "{""UserId"":""1""}"
  
  MySocket.SetFormData(Test_String)
  MySocket.Post("http://httpbin.org/post")

Use SetRequestContent instead of SetFormData:

DIM Test_String As String
Test_String = "{""UserId"":""1""}"
  
 MySocket.SetRequestContent(Test_String, "application/json")
 MySocket.Post("http://httpbin.org/post")