A new feature has been added to Indy Servers, now Server Push is supported by sgcWebSockets library.
HTTP usually works with Request/Response pattern, where client REQUEST a resource to SERVER and SERVER sends a RESPONSE with the resource requested or an error. Usually the client, like a browser, makes a bunch of requests for those assets which are provided by the server.
The main problem of this approach is that first client must send a request to get the resource, example: index.html, wait till server sends the response, the client reads the content and then make all other requests, example: styles.css
HTTP/2 server push tries to solve this problem, when the client requests a file, if server thinks that this file needs another file/s, those files will be PUSHED to client automatically.
HTTP/2 server push tries to solve this problem, when the client requests a file, if server thinks that this file needs another file/s, those files will be PUSHED to client automatically.
In the prior screenshot, first client request index.html, server reads this request and sends as a response 2 files: index.html and styles.css, so it avoids a second request to get styles.css
Configure Server Push
Following the prior screenshots, you can configure your server so every time there is a new request for /index.html file, server will send index.html and styles.css
Use the method PushPromiseAddPreLoadLinks, to associate every request to a push promise list.
Use the method PushPromiseAddPreLoadLinks, to associate every request to a push promise list.
server := TsgcWebSocketHTTPServer.Create(nil); oLinks := TStringList.Create; Try oLinks.Add('/styles.css'); server.PushPromiseAddPreLoadLinks('/index.html', oLinks); Finally oLinks.Free; End; procedure OnCommandGet(AContext: TIdContext; ARequestInfo: TIdHTTPRequestInfo; AResponseInfo: TIdHTTPResponseInfo); begin if ARequestInfo.Document = '/index.html' then begin AResponseInfo.ContentText := '<html></html>'; AResponseInfo.ContentType := 'text/html'; AResponseInfo.ResponseNo := 200; end else if ARequestInfo.Document = '/styles.css' then begin AResponseInfo.ContentText := '<style></style>'; AResponseInfo.ContentType := 'text/css'; AResponseInfo.ResponseNo := 200; end; end;
When the client request /index.html, automatically the server will send the 2 files, index.html and styles.css. You can check this behaviour using google chrome developer tools.