From the ArcGIS manual About Connecting to ArcGIS Server in ArcGIS for Desktop:
Specifying the server URL
Specifying the server URL When you connect, you'll be asked to type
the URL to your ArcGIS Server site. For user connections, you'll often
include the name of the ArcGIS Web Adaptor in your URL. This will look
For publisher and administrative connections, access through the web
adaptor is blocked by most organizations. Instead, you need to use the
administrative URL of the server, which takes the format
Some sites may require an HTTPS connection through port 6443. Check
with your server administrator if you are unsure of the appropriate
URL to use.
If you receive an error when connecting, one of more of the following
may be the cause:
- You typed an incorrect name or password.
- You did not use your server’s expected protocol of HTTP or HTTPS.
- You did not include the fully qualified domain name of the server (which is required in scenarios where the server is federated with
Portal for ArcGIS).
It is worth also to read the Compatibility of ArcGIS for server with earlier versions
Can I view and use my 10.6.1 services within an earlier version of
You can add 10.6.1 services to earlier versions of ArcGIS Desktop and
use them in the same way that you used them in the past, including as
a layer in ArcMap. However, if your ArcGIS Server10.6.1 site is
federated with Portal for ArcGIS and the portal is configured with
Security Assertion Markup Language (SAML), you must at least use
ArcGIS Desktop 10.3.
If your 10.6.1 ArcGIS Server site is federated with Portal for ArcGIS
and you are connecting from a pre-10.2 version of ArcGIS Desktop, you
must access your services through ArcMap using Add Data > Add Data
from Portal for ArcGIS. You cannot connect to the server by clicking
Add ArcGIS Server.