I have two AWS EC2 instances in the same VPC, Region, and Subnet. On instance A I have a very simple Web API setup in IIS on say port 12345. What I would like to do is have instance B be able to access the Web API on instance A without leaving the VPC. I have tried to access the API from instance B using the private IP (10.0.x.x:12345/api/) but it doesn’t work. Both servers are part of the same Security Group as well, and I have a rule allowing all traffic on all ports for the source 10.0.0.0/16. I know I am missing something, just not quite sure what. Any help or pointing me in the right direction is appreciated.