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.

#include <CkSocket.h>
#include <CkStringBuilder.h>

void ChilkatSample(void)
    {
    bool success = false;

    CkSocket socket;

    //  Connect to chilkatsoft.com over TLS.
    bool bTls = true;
    int maxWaitMs = 5000;
    success = socket.Connect("chilkatsoft.com",443,bTls,maxWaitMs);
    if (success == false) {
        std::cout << socket.lastErrorText() << "\r\n";
        return;
    }

    socket.put_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.
    const char *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) {
        std::cout << socket.lastErrorText() << "\r\n";
        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.
    const char *responseText = socket.receiveString();
    if (socket.get_LastMethodSuccess() == false) {
        std::cout << socket.lastErrorText() << "\r\n";
        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.
    CkStringBuilder sb;
    sb.Append(responseText);
    const char *contentLength = sb.getBetween("Content-Length: ","\r\n");
    if (sb.get_LastMethodSuccess() == false) {
        std::cout << sb.lastErrorText() << "\r\n";
        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.
    std::cout << "Characters received so far (headers + partial body): " << sb.get_Length() << "\r\n";
    std::cout << "Expected response body size (Content-Length): " << contentLength << " bytes" << "\r\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.
    }