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.

#import <CkoSocket.h>
#import <NSString.h>
#import <CkoStringBuilder.h>

BOOL success = NO;

CkoSocket *socket = [[CkoSocket alloc] init];

//  Connect to chilkatsoft.com over TLS.
BOOL bTls = YES;
int maxWaitMs = 5000;
success = [socket Connect: @"chilkatsoft.com" port: [NSNumber numberWithInt: 443] ssl: bTls maxWaitMs: [NSNumber numberWithInt: maxWaitMs]];
if (success == NO) {
    NSLog(@"%@",socket.LastErrorText);
    return;
}

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.
NSString *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 == NO) {
    NSLog(@"%@",socket.LastErrorText);
    return;
}

//  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.
NSString *responseText = [socket ReceiveString];
if (socket.LastMethodSuccess == NO) {
    NSLog(@"%@",socket.LastErrorText);
    return;
}

//  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.
CkoStringBuilder *sb = [[CkoStringBuilder alloc] init];
[sb Append: responseText];
NSString *contentLength = [sb GetBetween: @"Content-Length: " endMark: @"\r\n"];
if (sb.LastMethodSuccess == NO) {
    NSLog(@"%@",sb.LastErrorText);
    return;
}

//  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.
NSLog(@"%@%d",@"Characters received so far (headers + partial body): ",[sb.Length intValue]);
NSLog(@"%@%@%@",@"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.