From sgcWebSockets 4.1.3 a new WebSocket server is available, it's based on Microsoft HTTP Server API and it's available for Windows 8 and later. It's IOCP (Input Output Completion Ports) and asynchronous (non-blocking) based and can efficiently serve multiple clients (without using one thread per connection like Indy).
Example: if websocket connections are stablished in ws://127.0.0.1/ws url, just set server with these parameters (server requires admin rights to access to HTTP API).
oServer := TsgcWebSocketServer_HTTPAPI.Create(nil);
oServer.Active := True;