TCP Server in MAR
Here I read that tcp sockets not possible on mar:
All Application Instances are behind a load balancer that is designed to route HTTP requests. Therefore, it is not possible to create an application which is a server for raw TCP (or UDP) socket connections.
Can I use TCP server and TCP sockets with MAR or not?
No, you cannot use plain TCP sockets on MAR. The load balancers will only accept HTTP connections. In the example video also all traffic is on HTTP protocol.