About connecting to ArcGIS Server in ArcCatalog
ArcCatalog and the Catalog window in ArcMap allow two options for connecting to a GIS server: you can create either an administrative connection to manage GIS services, or a user connection to use GIS services.
When you connect as an administrator, you can use and edit the properties of all the services running on the server. You can also add, remove, start, stop, and pause services. Consequently, you must be running ArcCatalog as a member of the server's agsadmin group to make an administrative connection.
Using ArcCatalog, you can only make an administrative connection through a local area network. If you want to administer the server through the Internet, use ArcGIS Server Manager.
When you connect as a user, you can view and use the services on the server, but you cannot edit their properties or add, remove, start, stop, or pause services. When making a user connection, you can choose to connect to a local server running on the local area network (LAN) or a remote server over the Internet. You must be running ArcCatalog as a member of the server's agsusers group to make a user connection over the LAN.