This is not an ANet error but a gamestudio error. ANet errors are all self explaining and start with "ANet-Error:".
Maybe you forgot to copy a file into your project folder which is tried to be opened by the engine (this could also be some ANet related files). How ANet can be included into a project is descripted in the ANet manual.
ANet - A stable and secure network plugin with multi-zone, unlimited players, voip, server-list features,... (for A7/A8)!
get free version
