ReceiveString Returns Only the Immediately Available Data

See more Socket/SSL/TLS Examples

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.

-- Important: See this note about string length limitations for strings returned by sp_OAMethod calls.
--
CREATE PROCEDURE ChilkatSample
AS
BEGIN
    DECLARE @hr int
    DECLARE @iTmp0 int
    DECLARE @sTmp0 nvarchar(4000)
    DECLARE @success int
    SELECT @success = 0

    DECLARE @socket int
    EXEC @hr = sp_OACreate 'Chilkat.Socket', @socket OUT
    IF @hr <> 0
    BEGIN
        PRINT 'Failed to create ActiveX component'
        RETURN
    END

    --  Connect to chilkatsoft.com over TLS.
    DECLARE @bTls int
    SELECT @bTls = 1
    DECLARE @maxWaitMs int
    SELECT @maxWaitMs = 5000
    EXEC sp_OAMethod @socket, 'Connect', @success OUT, 'chilkatsoft.com', 443, @bTls, @maxWaitMs
    IF @success = 0
      BEGIN
        EXEC sp_OAGetProperty @socket, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @socket
        RETURN
      END

    EXEC sp_OASetProperty @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 ReceiveString against a public
    --  server -- for real HTTP work, use the Chilkat Http, Rest, or HttpCurl classes instead.
    DECLARE @httpReq nvarchar(4000)
    SELECT @httpReq = 'GET /big_helloWorld.txt HTTP/1.1' + CHAR(13) + CHAR(10) + 'Host: chilkatsoft.com' + CHAR(13) + CHAR(10) + 'Connection: close' + CHAR(13) + CHAR(10) + CHAR(13) + CHAR(10)
    EXEC sp_OAMethod @socket, 'SendString', @success OUT, @httpReq
    IF @success = 0
      BEGIN
        EXEC sp_OAGetProperty @socket, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @socket
        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.
    DECLARE @responseText nvarchar(4000)
    EXEC sp_OAMethod @socket, 'ReceiveString', @responseText OUT
    EXEC sp_OAGetProperty @socket, 'LastMethodSuccess', @iTmp0 OUT
    IF @iTmp0 = 0
      BEGIN
        EXEC sp_OAGetProperty @socket, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @socket
        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.
    DECLARE @sb int
    EXEC @hr = sp_OACreate 'Chilkat.StringBuilder', @sb OUT

    EXEC sp_OAMethod @sb, 'Append', @success OUT, @responseText
    DECLARE @contentLength nvarchar(4000)
    EXEC sp_OAMethod @sb, 'GetBetween', @contentLength OUT, 'Content-Length: ', CHAR(13) + CHAR(10)
    EXEC sp_OAGetProperty @sb, 'LastMethodSuccess', @iTmp0 OUT
    IF @iTmp0 = 0
      BEGIN
        EXEC sp_OAGetProperty @sb, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @socket
        EXEC @hr = sp_OADestroy @sb
        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.

    EXEC sp_OAGetProperty @sb, 'Length', @iTmp0 OUT
    PRINT 'Characters received so far (headers + partial body): ' + @iTmp0


    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.

    EXEC @hr = sp_OADestroy @socket
    EXEC @hr = sp_OADestroy @sb


END
GO