How to send custom command from client to server (LSP implementation)

Question

My implementation is based on 'vscode-languageserver' and I would like to know how to send custom requests to vscode server implementation.

Answer 1

server

const connection: LSP.IConnection = LSP.createConnection(LSP.ProposedFeatures.all);
connection.onNotification("handler/do", (handler)=>{});

client

let client:LanguageClient = <initialize>
client.sendNotification("handler/do");