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.

use strict;
use warnings;
use Chilkat2;

my $socket = Chilkat2::Socket->new;

# Connect to chilkatsoft.com over TLS.
my $bTls = 1;
my $maxWaitMs = 5000;
my $success = $socket->Connect('chilkatsoft.com', 443, $bTls, $maxWaitMs);
if (!$success) {
    print $socket->LastErrorText, "\n";
    exit;
}

$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 ReceiveString against a public
# server -- for real HTTP work, use the Chilkat Http, Rest, or HttpCurl classes instead.
my $httpReq = "GET /big_helloWorld.txt HTTP/1.1\r\nHost: chilkatsoft.com\r\nConnection: close\r\n\r\n";
$success = $socket->SendString($httpReq);
if (!$success) {
    print $socket->LastErrorText, "\n";
    exit;
}

# 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.
my $responseText = $socket->ReceiveString();
if (!$socket->LastMethodSuccess) {
    print $socket->LastErrorText, "\n";
    exit;
}

# 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.
my $sb = Chilkat2::StringBuilder->new;
$sb->Append($responseText);
my $contentLength = $sb->GetBetween('Content-Length: ', "\r\n");
if (!$sb->LastMethodSuccess) {
    print $sb->LastErrorText, "\n";
    exit;
}

# 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.
print 'Characters received so far (headers + partial body): ', $sb->Length, "\n";
print 'Expected response body size (Content-Length): ', $contentLength, " bytes\n";

# 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.