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.

#include <C_CkSocket.h>
#include <C_CkStringBuilder.h>

void ChilkatSample(void)
    {
    BOOL success;
    HCkSocket socket;
    BOOL bTls;
    int maxWaitMs;
    const char *httpReq;
    HCkStringBuilder sb;
    const char *contentLength;

    success = FALSE;

    socket = CkSocket_Create();

    //  Connect to chilkatsoft.com over TLS.
    bTls = TRUE;
    maxWaitMs = 5000;
    success = CkSocket_Connect(socket,"chilkatsoft.com",443,bTls,maxWaitMs);
    if (success == FALSE) {
        printf("%s\n",CkSocket_lastErrorText(socket));
        CkSocket_Dispose(socket);
        return;
    }

    CkSocket_putStringCharset(socket,"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.
    httpReq = "GET /big_helloWorld.txt HTTP/1.1\r\nHost: chilkatsoft.com\r\nConnection: close\r\n\r\n";
    success = CkSocket_SendString(socket,httpReq);
    if (success == FALSE) {
        printf("%s\n",CkSocket_lastErrorText(socket));
        CkSocket_Dispose(socket);
        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.
    sb = CkStringBuilder_Create();
    success = CkSocket_ReceiveSb(socket,sb);
    if (success == FALSE) {
        printf("%s\n",CkSocket_lastErrorText(socket));
        CkSocket_Dispose(socket);
        CkStringBuilder_Dispose(sb);
        return;
    }

    //  The response begins with HTTP headers.  The Content-Length header gives the total size, in bytes,
    //  of the response body.
    contentLength = CkStringBuilder_getBetween(sb,"Content-Length: ","\r\n");
    if (CkStringBuilder_getLastMethodSuccess(sb) == FALSE) {
        printf("%s\n",CkStringBuilder_lastErrorText(sb));
        CkSocket_Dispose(socket);
        CkStringBuilder_Dispose(sb);
        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.
    printf("Characters received so far (headers + partial body): %d\n",CkStringBuilder_getLength(sb));
    printf("Expected response body size (Content-Length): %s bytes\n",contentLength);

    //  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.


    CkSocket_Dispose(socket);
    CkStringBuilder_Dispose(sb);

    }