EMA C++ Developers Guide : 6 Consuming Data from the Cloud : 6.8 HTTP Error Handling for Reactor Token Reissues
 
6.8 HTTP Error Handling for Reactor Token Reissues
The Enterprise Message API supports handling for the following HTTP error codes from the API gateway:
300 Errors:
Perform URL redirect for 301, 302, 307 and 308 error codes
Retry the request to the API gateway for all other error codes
400 Errors:
For Version 1 authentication, retry with username and password for error codes 400 and 401
Stop retry the request for error codes 403, 404, 410, and 451
Retry the request to the API gateway for all other error codes
500 Errors:
Retry the request to the API gateway for all error codes