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.

local chilkat = require("chilkat")

local socket = chilkat.Socket.new()

-- Connect to chilkatsoft.com over TLS.
local bTls = true
local maxWaitMs = 5000
local success = socket:connect("chilkatsoft.com", 443, bTls, maxWaitMs)
if not success then
    print(socket.last_error_text)
    return
end

socket.string_charset = "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.
local httpReq = "GET /big_helloWorld.txt HTTP/1.1\r\nHost: chilkatsoft.com\r\nConnection: close\r\n\r\n"
success = socket:send_string(httpReq)
if not success then
    print(socket.last_error_text)
    return
end

-- 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.
local responseText = socket:receive_string()
if not socket.last_method_success then
    print(socket.last_error_text)
    return
end

-- 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.
local sb = chilkat.StringBuilder.new()
sb:append(responseText)
local contentLength = sb:get_between("Content-Length: ", "\r\n")
if not sb.last_method_success then
    print(sb.last_error_text)
    return
end

-- 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): " .. sb.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.