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 = false;

var socket = new CkSocket();

//  Connect to chilkatsoft.com over TLS.
var bTls = true;
var maxWaitMs = 5000;
success = socket.Connect("chilkatsoft.com",443,bTls,maxWaitMs);
if (success == false) {
    console.log(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.
var 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 == false) {
    console.log(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.
var responseText = socket.ReceiveString();
if (socket.LastMethodSuccess == false) {
    console.log(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.
var sb = new CkStringBuilder();
sb.Append(responseText);
var contentLength = sb.GetBetween("Content-Length: ","\r\n");
if (sb.LastMethodSuccess == false) {
    console.log(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.
console.log("Characters received so far (headers + partial body): " + sb.Length);
console.log("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.