TsgcWebSocketHTTPServer | HTTP/2 Server Push

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.

 

 

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.

 

TsgcWebSocketHTTPServer *server = new TsgcWebSocketHTTPServer(this);
TStringList *oLinks = new TStringList();
try
{
  oLinks->Add("/styles.css");
  server->PushPromiseAddPreLoadLinks("/index.html", oLinks);
}  
__finally
{
  oLinks->Free();
}
      
void OnCommandGet(TIdContext *AContext, TIdHTTPRequestInfo *ARequestInfo, TIdHTTPResponseInfo *AResponseInfo)
{
  if (ARequestInfo->Document == "/index.html")
  {
    AResponseInfo->ContentText = "";
    AResponseInfo->ContentType = "text/html";
    AResponseInfo->ResponseNo = 200;
  }
  else if (ARequestInfo->Document == "/styles.css")
  {
    AResponseInfo->ContentText = "";
    AResponseInfo->ContentType = "text/css";
    AResponseInfo->ResponseNo = 200;
  }
}

Using the chrome developer tool, you can view how the styles.css file is pushed to client.