ArcGIS Server Only Accessible From Local Machine

I have an ArcGIS server set up. It works, but only when I access the server (or server manager) via a web browser from the server machine itself. I am unable to access the server (using the same url) from another machine (Chrome: "This webpage is not available").

I have a website set up on the same domain (mydomain.edu), which works just fine. I am only having problems with the ArcGIS server (mydomain.edu:port_number/arcgis). Am I attempting to access this website incorrectly? Is there a setting which needs to be changed in order to allow remote access?

The main problem is that I want to be able to publish map services to the server remotely, which I am unable to do at the moment. ArcMap is unable to connect to the server.

Any advice from the gurus?