const char * vortex_frame_get_content_type ( VortexFrame frame  ) 

Returns frame content type.

Return actual frame's content type. The function always return a content type, either because it is defined or because default value is provided ("application/octet-stream").

Parameters:
frame The frame where the content type will be returned.
Returns:
The content type or NULL if the function fail (because the frame received is NULL or because the frame do not contains a MIME message).