A traditional proxy server is a server and a client. A server to the downstream clients, and a client to the backend servers.
Pub-Sub depends on the specific implementation. But anything with an open network socket listening for incoming connections I'd call the server, and anything making outbound connections I'd call the client. In some implementations only the broker is the server. In others every node is a server as they're all listening for multicast discovery messages.
Pub-Sub depends on the specific implementation. But anything with an open network socket listening for incoming connections I'd call the server, and anything making outbound connections I'd call the client. In some implementations only the broker is the server. In others every node is a server as they're all listening for multicast discovery messages.