In a server-side tagging setup, what protocol is typically used for sending event data from the client to the server container?

In a server-side tagging setup, the HTTP (Hypertext Transfer Protocol) protocol, and more specifically HTTPS (HTTP Secure), is typically used for sending event data from the client to the server container. HTTP is the foundation of data communication on the web, and HTTPS is its secure version, encrypting the data transmitted between the client and the server to protect it from eavesdropping. The client, usually a web browser or a mobile app, sends data to the server container using HTTP requests, most commonly POST requests. A POST request allows the client to send data to the server in the body of the request. The server container, which is hosted on a platform like Google Cloud Platform (GCP), receives these HTTP requests and processes the data accordingly. While other protocols exist, HTTP/HTTPS is preferred because it's the standard protocol for web communication, is widely supported by browsers and servers, and integrates seamlessly with web infrastructure. The 'Measurement Protocol' is also used to send data, which is just a specific implementation using HTTP requests. It allows developers to send data directly to Google Analytics servers. Therefore, the combination of HTTP/HTTPS and the Measurement Protocol is the standard approach for sending event data from the client to the server container in a server-side tagging environment.