How do servers communicate? Web browsers and servers communicate using TCP/IP. Hypertext Transfer Protocol is the standard application protocol on top of TCP/IP supporting web browser requests and server responses.
Can a server be a client? A server is a computer or system that provides resources, data, services, or programs to other computers, known as clients, over a network.
How servers connect to each other? Servers are uniquely connected to a network, via a network switch (I won’t detail all the different topologies and components of each) for user connectivity. It is common to have servers clustered over a shared network but this is not done on a global application for all servers in a data center.
How can 2 servers communicate? For a basic solution you can use Socket.IO if you are already using it and know how it works, it will get the job done since it allows for communication between a client and server where the client can be a different server in a different language.