The following error response codes could be generated (in JSON or XML):
1 An unknown error occurred. Please resubmit the request.
2 The service is not available at this time.
4 The application has reached the maximum number of requests allowed. More requests are allowed once the time window has completed.
5 The request came from a remote address not allowed by this application.
101 The API key submitted is not associated with any known application.
102 The session key was improperly submitted or has reached its timeout. Direct the user to log in again to obtain another key.
103 The submitted call_id was not greater than the previous call_id for this session.
104 Incorrect signature.