I am answering my own question based. I found the answer after doing WAY too much searching via google.
My server (a new Amazon EC2 - Windows 2012 instance) had Windows Firewall enabled and was blocking port 5003 for the local domain. To remove the block, from the Windows Firewall control panel, I selected "inbound" and added a new "port" rule allowing access for port 5003.
NOTE: I had already configured the Amazon EC2 Security Group for the server to allow traffic for port 5003 (and HTTP and HTTPS too).