ReceiveString Returns Only the Immediately Available Data

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Demonstrates that Socket.ReceiveString returns only the text 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 ReceiveString 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: Boolean;
socket: HCkSocket;
bTls: Boolean;
maxWaitMs: Integer;
httpReq: PWideChar;
responseText: PWideChar;
sb: HCkStringBuilder;
contentLength: PWideChar;

begin
success := False;

socket := CkSocket_Create();

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

CkSocket_putStringCharset(socket,'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 ReceiveString 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 := CkSocket_SendString(socket,httpReq);
if (success = False) then
  begin
    Memo1.Lines.Add(CkSocket__lastErrorText(socket));
    Exit;
  end;

//  Call ReceiveString a single time.  It returns only the text that is immediately available --
//  typically just the first network packet -- and does NOT wait for the entire response to arrive.
responseText := CkSocket__receiveString(socket);
if (CkSocket_getLastMethodSuccess(socket) = False) then
  begin
    Memo1.Lines.Add(CkSocket__lastErrorText(socket));
    Exit;
  end;

//  Load the received text into a StringBuilder so its length can be measured and the Content-Length
//  header extracted.  The Content-Length header gives the total size, in bytes, of the response body.
sb := CkStringBuilder_Create();
CkStringBuilder_Append(sb,responseText);
contentLength := CkStringBuilder__getBetween(sb,'Content-Length: ',#13#10);
if (CkStringBuilder_getLastMethodSuccess(sb) = False) then
  begin
    Memo1.Lines.Add(CkStringBuilder__lastErrorText(sb));
    Exit;
  end;

//  Compare what this single ReceiveString 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(CkStringBuilder_getLength(sb)));
Memo1.Lines.Add('Expected response body size (Content-Length): ' + contentLength + ' bytes');

//  A single ReceiveString 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.

CkSocket_Dispose(socket);
CkStringBuilder_Dispose(sb);