Why is the service only accessible from the outside if you first open it on localhost?

Question

linux

Hi, help, I'm scratching my head.
There is an old asmx service written many years ago, written in c# for dotnet. Then there was a move to Centos.
From worked under Centos 7, installed mono 6.0.0, xsp - everything works. I once did this under Tsar Peas, there were no questions.
Now I installed it from scratch on a new server - everything seems to be the same, Centos 7, mono, though newer - 6.8, transferred the service - and for some reason, in order for everything to work, I first need to open this service in a browser on localhost - After that, everything becomes normal from the outside. If you do not open it, the service is not visible from the outside.
Tell me what it could be and in which direction I should dig - the server, the system, or the mono itself ... firewalld is disabled, the iptables rules have been removed, everything is open.

Answer 1

Disable selinux