Understanding the Language Server Protocol
In the past, many code editors were built just for the specific language, and to provide rich and smart code editing, tight integration between the editor and the language tooling was a must. On the other hand, there were (and still are) more general-purpose editors, but they lacked in functionality when it came to more advanced language-specific features like code completion, “go to definition”, etc. (for example, code highlighting was done using the regular expressions).
But then Microsoft introduced the Language Server Protocol (LSP) as a solution to the problem above, which elegantly transforms this M*N complexity into a more manageable M+N situation.
The Language Server Protocol is built upon JSON-RPC. It specifically uses JSON RPC 2.0. You can think of JSON-RPC as a remote procedure call protocol that uses JSON for data encoding.
In a nutshell, it works like this. First, the editor establishes a connection with the language server, then as the developer types code, the editor sends incremental changes to the language server. It then sends back insights like: code completion suggestions, diagnostics.
