ReceiveSb Returns Only the Immediately Available Data

See more Socket/SSL/TLS Examples

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.

IncludeFile "CkStringBuilder.pb"
IncludeFile "CkSocket.pb"

Procedure ChilkatExample()

    success.i = 0

    socket.i = CkSocket::ckCreate()
    If socket.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    ;  Connect to chilkatsoft.com over TLS.
    bTls.i = 1
    maxWaitMs.i = 5000
    success = CkSocket::ckConnect(socket,"chilkatsoft.com",443,bTls,maxWaitMs)
    If success = 0
        Debug CkSocket::ckLastErrorText(socket)
        CkSocket::ckDispose(socket)
        ProcedureReturn
    EndIf

    CkSocket::setCkStringCharset(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.s = "GET /big_helloWorld.txt HTTP/1.1" + Chr(13) + Chr(10) + "Host: chilkatsoft.com" + Chr(13) + Chr(10) + "Connection: close" + Chr(13) + Chr(10) + Chr(13) + Chr(10)
    success = CkSocket::ckSendString(socket,httpReq)
    If success = 0
        Debug CkSocket::ckLastErrorText(socket)
        CkSocket::ckDispose(socket)
        ProcedureReturn
    EndIf

    ;  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.i = CkStringBuilder::ckCreate()
    If sb.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkSocket::ckReceiveSb(socket,sb)
    If success = 0
        Debug CkSocket::ckLastErrorText(socket)
        CkSocket::ckDispose(socket)
        CkStringBuilder::ckDispose(sb)
        ProcedureReturn
    EndIf

    ;  The response begins with HTTP headers.  The Content-Length header gives the total size, in bytes,
    ;  of the response body.
    contentLength.s = CkStringBuilder::ckGetBetween(sb,"Content-Length: ",Chr(13) + Chr(10))
    If CkStringBuilder::ckLastMethodSuccess(sb) = 0
        Debug CkStringBuilder::ckLastErrorText(sb)
        CkSocket::ckDispose(socket)
        CkStringBuilder::ckDispose(sb)
        ProcedureReturn
    EndIf

    ;  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.
    Debug "Characters received so far (headers + partial body): " + Str(CkStringBuilder::ckLength(sb))
    Debug "Expected response body size (Content-Length): " + contentLength + " bytes"

    ;  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::ckDispose(socket)
    CkStringBuilder::ckDispose(sb)


    ProcedureReturn
EndProcedure