(SQL Server) (Deprecated) Asynchronous Sockets

Notice: The functionality described here is deprecated and replaced by a newer model for asynchronous method calls. The newer model was introduced in Chilkat v9.5.0.52, and is identified by methods having names ending in “Async” which return a task object.

Discusses how asynchronous sockets (in Chilkat) are used for reading, writing, connecting, and accepting connections. The same code works for both SSL/TLS and non-SSL/TLS (unencrypted) sockets.

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

-- 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
    -- Important: Do not use nvarchar(max).  See the warning about using nvarchar(max).
    DECLARE @sTmp0 nvarchar(4000)
    -- Notice: The functionality described here is deprecated and replaced 
    -- by a newer model for asynchronous method calls. The newer model was 
    -- introduced in Chilkat v9.5.0.52, and is identified by methods 
    -- having names ending in “Async” which return a task object.

    -- This example requires the Chilkat API to have been previously unlocked.
    -- See Global Unlock Sample for sample code.

    DECLARE @socket int
    -- Use "Chilkat_9_5_0.Socket" for versions of Chilkat < 10.0.0
    EXEC @hr = sp_OACreate 'Chilkat.Socket', @socket OUT
    IF @hr <> 0
    BEGIN
        PRINT 'Failed to create ActiveX component'
        RETURN
    END

    DECLARE @success int

    DECLARE @useSsl int
    SELECT @useSsl = 0
    DECLARE @maxWaitMillisec int
    SELECT @maxWaitMillisec = 20000

    -- The remote hostname may be an IP address, a domain name,
    -- or "localhost".  You'll need to change this:
    DECLARE @remoteHost nvarchar(4000)

    SELECT @remoteHost = '123.123.88.88'
    DECLARE @remotePort int
    SELECT @remotePort = 8125

    -- The meaning of "asynchronous" is that the socket operation, whether
    -- it be a read, write, connect, or accept, happens in a background
    -- thread and thus leaves your application free to do something
    -- else while the socket operation is running.
    -- 
    -- Note: If your application is simply going to initiate an asynchronous operation
    -- and do nothing except wait for it to complete, then it may as
    -- well use the synchronous socket methods -- there's no point in adding 
    -- complexity to your application if it's not necessary.  The meaning of "synchronous" 
    -- is that the method call (for reading, writing, connecting, accepting) does not 
    -- return until the socket operation is complete.
    -- 
    -- All asynchronous socket operations follow these basic steps:
    -- 1) Initiate the asynchronous socket operation.  This starts a background thread
    -- that does the work. The method called to initiate the asynchronous operation
    -- returns immediately.
    -- 2) Wait until the operation is completed by periodically examining the 
    -- "Finished" property.  Each type of socket operation has it's own "Finished" property, such as AsyncReceiveFinished.
    -- Once it becomes 1 or 0, you may check the "Success" property (see next step).
    -- 3) Once finished, you may check the "Success" property to see if the asynchronous operation 
    -- succeeded or failed.  Each type of socket operation has it's own "Success" property,
    -- such as AsynchReceiveSuccess.
    -- 4) If it failed, the error information is available in the "Log" property, such as "AsyncReceiveLog".
    -- 5) If success, then the return data is available in another property (see below).

    -- -------------------------------------------------------------------------
    -- Asynchronous Socket Methods and Properties
    -- -------------------------------------------------------------------------
    -- 
    -- --------------------
    -- Receiving Data:
    -- --------------------
    -- 
    --  Methods for initiating a background receive:  
    --     AsyncReceiveBytes
    --     AsyncReceiveBytesN
    --     AsyncReceiveString
    --     AsyncReceiveToCRLF
    --     AsyncReceiveUntilMatch
    --  Properties:
    --     AsyncReceiveFinished - Becomes 1 when completed.
    --     AsyncReceiveSuccess - Set to 1 or 0 when finished.
    --      AsyncReceiveLog - Error information if failed.
    --     AsyncReceivedBytes - Data received if receiving binary data.
    --      AsyncReceivedString -- Data received if receiving a string.
    -- 
    -- --------------------
    -- Sending Data:
    -- --------------------
    -- 
    -- Methods for initiating a background send:
    --     AsyncSendBytes
    --     AsyncSendString
    -- Properties:
    --     AsyncSendFinished - Becomes 1 when completed.
    --     AsyncSendSuccess - Set to 1 or 0 when finished.
    --      AsyncSendLog - Error information if failed.

    -- --------------------
    -- Making a TCP Connection:
    -- --------------------
    -- 
    -- Method for initiating a background connect:
    --     AsyncConnectStart
    -- Properties:
    --     AsyncConnectFinished - Becomes 1 when completed.
    --     AsyncConnectSuccess - Set to 1 or 0 when finished.
    --      AsyncConnectLog - Error information if failed.

    -- --------------------
    -- Accepting an Incoming a TCP Connection:
    -- --------------------
    -- 
    -- Method for initiating a background accept:
    --     AsyncAcceptStart
    -- Properties:
    --     AsyncAcceptFinished - Becomes 1 when completed.
    --     AsyncAcceptSuccess - Set to 1 or 0 when finished.
    --      AsyncAcceptLog - Error information if failed.
    -- 
    -- ** After AsyncAcceptFinished becomes 1 *and* AsyncAcceptSuccess
    -- is 1, the connected socket may be retrieved by calling AsyncAcceptSocket.

    -- --------------------
    -- DNS Lookup
    -- --------------------
    -- 
    -- Method for initiating a background DNS lookup:
    --     AsyncDnsStart
    -- Properties:
    --     AsyncDnsFinished - Becomes 1 when completed.
    --     AsyncDnsSuccess - Set to 1 or 0 when finished.
    --      AsyncDnsLog - Error information if failed.
    --      AsyncDnsResult - The IP address of the DNS lookup if successful.

    -- The following code demonstrates connecting, sending, and receiving asynchronously.
    -- NOTE: This example simply waits for each background operation
    -- to complete.  In general, the whole point of doing something
    -- asynchronously is so your application is free to do other things,
    -- such as manage the user-interface.  

    -- Connect to the remote host asynchronously in a background thread.
    EXEC sp_OAMethod @socket, 'AsyncConnectStart', @success OUT, @remoteHost, @remotePort, @useSsl, @maxWaitMillisec
    IF @success <> 1
      BEGIN
        EXEC sp_OAGetProperty @socket, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @socket
        RETURN
      END

    -- Wait for the socket to become connected...
    EXEC sp_OAGetProperty @socket, 'AsyncConnectFinished', @iTmp0 OUT
    WHILE (@iTmp0 <> 1)
      BEGIN
        -- Sleep 1 second.
        EXEC sp_OAMethod @socket, 'SleepMs', NULL, 100
      END

    -- Did the connect fail?
    EXEC sp_OAGetProperty @socket, 'AsyncConnectSuccess', @iTmp0 OUT
    IF @iTmp0 <> 1
      BEGIN
        EXEC sp_OAGetProperty @socket, 'AsyncConnectLog', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @socket
        RETURN
      END

    -- Set maximum timeouts for reading an writing (in millisec)
    EXEC sp_OASetProperty @socket, 'MaxReadIdleMs', 20000
    EXEC sp_OASetProperty @socket, 'MaxSendIdleMs', 20000

    -- Send a "Hello Server! -EOM-" message:
    EXEC sp_OAMethod @socket, 'AsyncSendString', @success OUT, 'Hello Server! -EOM-'
    IF @success <> 1
      BEGIN
        EXEC sp_OAGetProperty @socket, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @socket
        RETURN
      END

    -- Wait for the send to finish
    EXEC sp_OAGetProperty @socket, 'AsyncSendFinished', @iTmp0 OUT
    WHILE (@iTmp0 <> 1)
      BEGIN
        -- Sleep 1 second.
        EXEC sp_OAMethod @socket, 'SleepMs', NULL, 100
      END

    -- Did the send fail?
    EXEC sp_OAGetProperty @socket, 'AsyncSendSuccess', @iTmp0 OUT
    IF @iTmp0 <> 1
      BEGIN
        EXEC sp_OAGetProperty @socket, 'AsyncSendLog', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @socket
        RETURN
      END

    -- The server (in this example) is going to send a "Hello Client! -EOM-" 
    -- message.  Begin reading asynchronously in a background thread:
    EXEC sp_OAMethod @socket, 'AsyncReceiveUntilMatch', @success OUT, '-EOM-'
    IF @success <> 1
      BEGIN
        EXEC sp_OAGetProperty @socket, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @socket
        RETURN
      END

    -- Wait for the background read to finish
    EXEC sp_OAGetProperty @socket, 'AsyncReceiveFinished', @iTmp0 OUT
    WHILE (@iTmp0 <> 1)
      BEGIN
        -- Sleep 1 second.
        EXEC sp_OAMethod @socket, 'SleepMs', NULL, 100
      END

    -- Did the receive fail?
    EXEC sp_OAGetProperty @socket, 'AsyncReceiveSuccess', @iTmp0 OUT
    IF @iTmp0 <> 1
      BEGIN
        EXEC sp_OAGetProperty @socket, 'AsyncReceiveLog', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @socket
        RETURN
      END

    -- Display the received message:
    EXEC sp_OAGetProperty @socket, 'AsyncReceivedString', @sTmp0 OUT
    PRINT @sTmp0

    -- Close the connection with the server
    -- Wait a max of 20 seconds (20000 millsec)
    EXEC sp_OAMethod @socket, 'Close', @success OUT, 20000

    EXEC @hr = sp_OADestroy @socket


END
GO