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.

integer li_rc
integer li_Success
oleobject loo_Socket
integer li_BTls
integer li_MaxWaitMs
string ls_HttpReq
oleobject loo_Sb
string ls_ContentLength

li_Success = 0

loo_Socket = create oleobject
li_rc = loo_Socket.ConnectToNewObject("Chilkat.Socket")
if li_rc < 0 then
    destroy loo_Socket
    MessageBox("Error","Connecting to COM object failed")
    return
end if

//  Connect to chilkatsoft.com over TLS.
li_BTls = 1
li_MaxWaitMs = 5000
li_Success = loo_Socket.Connect("chilkatsoft.com",443,li_BTls,li_MaxWaitMs)
if li_Success = 0 then
    Write-Debug loo_Socket.LastErrorText
    destroy loo_Socket
    return
end if

loo_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 ReceiveSb against a public
//  server -- for real HTTP work, use the Chilkat Http, Rest, or HttpCurl classes instead.
ls_HttpReq = "GET /big_helloWorld.txt HTTP/1.1~r~nHost: chilkatsoft.com~r~nConnection: close~r~n~r~n"
li_Success = loo_Socket.SendString(ls_HttpReq)
if li_Success = 0 then
    Write-Debug loo_Socket.LastErrorText
    destroy loo_Socket
    return
end if

//  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.
loo_Sb = create oleobject
li_rc = loo_Sb.ConnectToNewObject("Chilkat.StringBuilder")

li_Success = loo_Socket.ReceiveSb(loo_Sb)
if li_Success = 0 then
    Write-Debug loo_Socket.LastErrorText
    destroy loo_Socket
    destroy loo_Sb
    return
end if

//  The response begins with HTTP headers.  The Content-Length header gives the total size, in bytes,
//  of the response body.
ls_ContentLength = loo_Sb.GetBetween("Content-Length: ","~r~n")
if loo_Sb.LastMethodSuccess = 0 then
    Write-Debug loo_Sb.LastErrorText
    destroy loo_Socket
    destroy loo_Sb
    return
end if

//  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.
Write-Debug "Characters received so far (headers + partial body): " + string(loo_Sb.Length)
Write-Debug "Expected response body size (Content-Length): " + ls_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.


destroy loo_Socket
destroy loo_Sb