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.

import sys
import chilkat

success = False

socket = chilkat.CkSocket()

#  Connect to chilkatsoft.com over TLS.
bTls = True
maxWaitMs = 5000
success = socket.Connect("chilkatsoft.com",443,bTls,maxWaitMs)
if (success == False):
    print(socket.lastErrorText())
    sys.exit()

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.
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):
    print(socket.lastErrorText())
    sys.exit()

#  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.
responseText = socket.receiveString()
if (socket.get_LastMethodSuccess() == False):
    print(socket.lastErrorText())
    sys.exit()

#  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.
sb = chilkat.CkStringBuilder()
sb.Append(responseText)
contentLength = sb.getBetween("Content-Length: ","\r\n")
if (sb.get_LastMethodSuccess() == False):
    print(sb.lastErrorText())
    sys.exit()

#  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.
print("Characters received so far (headers + partial body): " + str(sb.get_Length()))
print("Expected response body size (Content-Length): " + contentLength + " bytes")

#  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.