3.3 WOPI Protocol Server Details
The WOPI server responds to WOPI requests from WOPI clients. It returns information about files and file content in its responses. The WOPI server never initiates communication with the WOPI client.
Except where specified, WOPI clients SHOULD interpret HTTP Status-Codes returned by the WOPI server as specified in [RFC2616] section 10, "Status Code Definitions."