The analysis server is run by executing the dart language_server command, which is implemented in the dartdev package. That command invokes the main function in bin/server.dart. The only thing main does is to create an instance of ServerStarter and pass the command-line arguments to it.

The starter interprets the command-line arguments in order to create and initialize an AnalysisServer.

Even though the command-line tools don't use it that way, the analysis server is designed to be a long-lived process.

The server communicates with a single client (the process that started the server) using one of two wire protocols: a legacy protocol, which is used to support IntelliJ and Android Studio, and LSP (the Language Server Protocol from Microsoft), which is used to support VS Code and several other IDEs and editors. The protocol is selected at start-up via command-line arguments.

To learn more about how the server communicates with the client, you can read about either LSP or the legacy protocol.

Based on the selected protocol, the starter creates an instance of one of the two concrete subclasses of AnalysisServer, either LspAnalysisServer or LegacyAnalysisServer, and initializes it.

To learn how the server implements support for the protocols, read about the request handlers.