ReceiveSb Returns Only the Immediately Available Data

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Demonstrates that Socket.ReceiveSb returns only the data immediately available and not the entire response. The example connects to chilkatsoft.com over TLS and requests big_helloWorld.txt, a large text file of roughly 74,000 lines. A single ReceiveSb call returns just the first portion of the response, and the example reports how many characters were received compared with the total size given by the response Content-Length header.

var
success: Integer;
socket: TChilkatSocket;
bTls: Integer;
maxWaitMs: Integer;
httpReq: WideString;
sb: TChilkatStringBuilder;
contentLength: WideString;

begin
success := 0;

socket := TChilkatSocket.Create(Self);

//  Connect to chilkatsoft.com over TLS.
bTls := 1;
maxWaitMs := 5000;
success := socket.Connect('chilkatsoft.com',443,bTls,maxWaitMs);
if (success = 0) then
  begin
    Memo1.Lines.Add(socket.LastErrorText);
    Exit;
  end;

socket.StringCharset := 'utf-8';

//  Send an HTTP GET request for big_helloWorld.txt, a large text file of roughly 74,000 lines of
//  "Hello World!".  This uses a minimal HTTP request only to exercise ReceiveSb against a public
//  server -- for real HTTP work, use the Chilkat Http, Rest, or HttpCurl classes instead.
httpReq := 'GET /big_helloWorld.txt HTTP/1.1' + #13#10 + 'Host: chilkatsoft.com' + #13#10 + 'Connection: close' + #13#10 + #13#10;
success := socket.SendString(httpReq);
if (success = 0) then
  begin
    Memo1.Lines.Add(socket.LastErrorText);
    Exit;
  end;

//  Call ReceiveSb a single time.  It returns only the bytes that are immediately available --
//  typically just the first network packet -- and does NOT wait for the entire response to arrive.
sb := TChilkatStringBuilder.Create(Self);
success := socket.ReceiveSb(sb.ControlInterface);
if (success = 0) then
  begin
    Memo1.Lines.Add(socket.LastErrorText);
    Exit;
  end;

//  The response begins with HTTP headers.  The Content-Length header gives the total size, in bytes,
//  of the response body.
contentLength := sb.GetBetween('Content-Length: ',#13#10);
if (sb.LastMethodSuccess = 0) then
  begin
    Memo1.Lines.Add(sb.LastErrorText);
    Exit;
  end;

//  Compare what this single ReceiveSb returned against the full size of the expected response.  The
//  received amount is only a small fraction of the total.
Memo1.Lines.Add('Characters received so far (headers + partial body): ' + IntToStr(sb.Length));
Memo1.Lines.Add('Expected response body size (Content-Length): ' + contentLength + ' bytes');

//  A single ReceiveSb call returns whatever is currently available, so it cannot indicate whether the
//  full response has arrived.  This makes it difficult to know when a response is complete: the
//  application must either know how many bytes to expect (for example from a Content-Length header or
//  an application-defined length prefix) and keep receiving until that many bytes are collected, or
//  keep receiving until the peer closes the connection.