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.

load ./chilkat.dll

set success 0

set socket [new_CkSocket]

#  Connect to chilkatsoft.com over TLS.
set bTls 1
set maxWaitMs 5000
set success [CkSocket_Connect $socket "chilkatsoft.com" 443 $bTls $maxWaitMs]
if {$success == 0} then {
    puts [CkSocket_lastErrorText $socket]
    delete_CkSocket $socket
    exit
}

CkSocket_put_StringCharset $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.
set httpReq "GET /big_helloWorld.txt HTTP/1.1\r\nHost: chilkatsoft.com\r\nConnection: close\r\n\r\n"
set success [CkSocket_SendString $socket $httpReq]
if {$success == 0} then {
    puts [CkSocket_lastErrorText $socket]
    delete_CkSocket $socket
    exit
}

#  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.
set sb [new_CkStringBuilder]

set success [CkSocket_ReceiveSb $socket $sb]
if {$success == 0} then {
    puts [CkSocket_lastErrorText $socket]
    delete_CkSocket $socket
    delete_CkStringBuilder $sb
    exit
}

#  The response begins with HTTP headers.  The Content-Length header gives the total size, in bytes,
#  of the response body.
set contentLength [CkStringBuilder_getBetween $sb "Content-Length: " "\r\n"]
if {[CkStringBuilder_get_LastMethodSuccess $sb] == 0} then {
    puts [CkStringBuilder_lastErrorText $sb]
    delete_CkSocket $socket
    delete_CkStringBuilder $sb
    exit
}

#  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.
puts "Characters received so far (headers + partial body): [CkStringBuilder_get_Length $sb]"
puts "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.

delete_CkSocket $socket
delete_CkStringBuilder $sb