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.

let socket = chilkat::Socket::new();

// Connect to chilkatsoft.com over TLS.
let b_tls = true;
let max_wait_ms = 5000;
if socket.connect("chilkatsoft.com", 443, b_tls, max_wait_ms).is_err() {
    println!("{}", socket.last_error_text());
    return;
}

socket.set_string_charset("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.
let http_req = "GET /big_helloWorld.txt HTTP/1.1\r\nHost: chilkatsoft.com\r\nConnection: close\r\n\r\n".to_string();
if socket.send_string(&http_req).is_err() {
    println!("{}", socket.last_error_text());
    return;
}

// 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.
let sb = chilkat::StringBuilder::new();
if socket.receive_sb(&sb).is_err() {
    println!("{}", socket.last_error_text());
    return;
}

// The response begins with HTTP headers.  The Content-Length header gives the total size, in bytes,
// of the response body.
let Ok(content_length) = sb.get_between("Content-Length: ", "\r\n") else {
    println!("{}", sb.last_error_text());
    return;
};

// 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.
println!("Characters received so far (headers + partial body): {}", sb.length());
println!("Expected response body size (Content-Length): {} bytes", content_length);

// 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.