Unable to create an ArcGIS Server connection from ArcMap

Description

When creating a connection from ArcMap to ArcGIS Server, the connection fails and returns various errors, but not limited to:

Error:   
Access to this resource is forbidden, regardless of authorization. (status code 403).

Error:   
No resource could be found at that address. (status code 404).

Error:   
Proxy server got bad address from remote server (verify the server is running). (status code 504).

Error:   
Username and password are required.

Cause

The following are possible causes:

• An incorrect port is used.
• Incorrect credentials are used.
• A firewall is preventing the connection.

Solution or Workaround

Follow one of the options below depending on the cause to resolve the issue.

Use the correct port

To create an ArcGIS Server connection in ArcMap, use HTTPS port 6443 instead of HTTP port 6080 for Server URL. For example, https://gisserver.domain.com:6443/arcgis. Refer to ArcGIS Server: Components of ArcGIS URLs for more information.

Note:
To enable the use of HTTP port 6080, administrators can change the setting in ArcGIS Server Administrator Directory to allow HTTP plaintext communication through the port, however it is a less secure option. Refer to ArcGIS Server: Secure ArcGIS Server communication for more information.

Use the correct credentials

Check if the ArcGIS Server site is federated with a portal. If it is federated with a portal, use the Portal credentials. Refer to ArcGIS Server: Federate an ArcGIS Server site with your portal for more information.

The following image displays a successful ArcGIS Server connection in ArcMap.

Configure the firewall settings

To allow a connection to ArcGIS Server, remove the firewall rule on the machine blocking the connection. Refer to How To: Configure ArcGIS Server for firewalls and NAT devices for more information.