SQL Server

Send and Receive WebSocket Messages

See more WebSocket Examples

This example how to send and receive websocket messages.

A WebSocket message can be composed of one or more frames. The simple case is where a single frame is both the first and last frame in a message. This is the case where the 1st frame in the message has the "final frame" bit set.

This example demonstrates sending and receiving multi-frame messages.

Note: The websockets.chilkat.io server imposes the following limitations:
Messages must be 16K or less, and each connection is limited to a max of 16 echoed messages.

SQL Server

-- 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)
    DECLARE @success int
    SELECT @success = 0

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

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

    -- For brevity, this example does not check for errors when etablishing the WebSocket connection.
    -- See Establish WebSocket Connection for more complete sample code for making the connection.

    DECLARE @rest int
    EXEC @hr = sp_OACreate 'Chilkat.Rest', @rest OUT

    -- Connect to websockets.chilkat.io
    -- IMPORTANT: websockets.chilkat.io accepts frames of up to 16K in size and echoes them back.
    -- IMPORTANT: The websockets.chilkat.io server imposes the following limitations: 
    -- ---------- Messages must be 16K or less, and each connection is limited to a max of 16 echoed messages.
    EXEC sp_OAMethod @rest, 'Connect', @success OUT, 'websockets.chilkat.io', 80, 0, 0
    EXEC sp_OAMethod @ws, 'UseConnection', @success OUT, @rest
    EXEC sp_OAMethod @ws, 'AddClientHeaders', @success OUT
    DECLARE @responseBodyIgnored nvarchar(4000)
    EXEC sp_OAMethod @rest, 'FullRequestNoBody', @responseBodyIgnored OUT, 'GET', '/wsChilkatEcho.ashx'
    EXEC sp_OAMethod @ws, 'ValidateServerHandshake', @success OUT
    IF @success <> 1
      BEGIN
        EXEC sp_OAGetProperty @ws, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @ws
        EXEC @hr = sp_OADestroy @rest
        RETURN
      END

    -- This example demonstrates sending and receiving a multi-frame message.

    -- The websocket message will be composed of three text lines, each frame will contain a single line.

    -- Send the 1st frame in the message.
    DECLARE @finalFrame int
    SELECT @finalFrame = 0
    EXEC sp_OAMethod @ws, 'SendFrame', @success OUT, 'This is the 1st frame' + CHAR(13) + CHAR(10), @finalFrame
    IF @success <> 1
      BEGIN
        EXEC sp_OAGetProperty @ws, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @ws
        EXEC @hr = sp_OADestroy @rest
        RETURN
      END

    -- Send the 2nd frame in the message.
    EXEC sp_OAMethod @ws, 'SendFrame', @success OUT, 'This is the 2nd frame' + CHAR(13) + CHAR(10), @finalFrame
    IF @success <> 1
      BEGIN
        EXEC sp_OAGetProperty @ws, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @ws
        EXEC @hr = sp_OADestroy @rest
        RETURN
      END

    -- Send the 3rd and final frame in the message.
    SELECT @finalFrame = 1
    EXEC sp_OAMethod @ws, 'SendFrame', @success OUT, 'This is the 3rd frame' + CHAR(13) + CHAR(10), @finalFrame
    IF @success <> 1
      BEGIN
        EXEC sp_OAGetProperty @ws, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @ws
        EXEC @hr = sp_OADestroy @rest
        RETURN
      END

    -- Read an incoming frames until we receive the final frame.
    -- Note: It may be that the echo server (websockets.chilkat.io) responds with 
    -- the full message in a single final frame.
    DECLARE @receivedFinalFrame int
    SELECT @receivedFinalFrame = 0
    WHILE @receivedFinalFrame = 0
      BEGIN

        EXEC sp_OAMethod @ws, 'ReadFrame', @success OUT
        IF @success <> 1
          BEGIN

            PRINT 'Failed to receive a frame'

            EXEC sp_OAGetProperty @ws, 'ReadFrameFailReason', @iTmp0 OUT
            PRINT 'ReadFrame fail reason = ' + @iTmp0
            EXEC sp_OAGetProperty @ws, 'LastErrorText', @sTmp0 OUT
            PRINT @sTmp0
            EXEC @hr = sp_OADestroy @ws
            EXEC @hr = sp_OADestroy @rest
            RETURN
          END

        EXEC sp_OAGetProperty @ws, 'FinalFrame', @receivedFinalFrame OUT

        -- Show the opcode and final frame bit for the frame just received:

        EXEC sp_OAGetProperty @ws, 'FrameOpcode', @sTmp0 OUT
        PRINT 'Frame opcode: ' + @sTmp0

        PRINT 'Final frame: ' + @receivedFinalFrame
      END

    -- Return the message accumulated in the above calls to ReadFrame.
    DECLARE @receivedMsg nvarchar(4000)
    EXEC sp_OAMethod @ws, 'GetFrameData', @receivedMsg OUT

    PRINT 'Received: ' + @receivedMsg

    -- Close the websocket connection.
    EXEC sp_OAMethod @ws, 'SendClose', @success OUT, 1, 1000, 'Closing this websocket.'
    IF @success <> 1
      BEGIN
        EXEC sp_OAGetProperty @ws, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @ws
        EXEC @hr = sp_OADestroy @rest
        RETURN
      END

    -- Read the Close response.
    EXEC sp_OAMethod @ws, 'ReadFrame', @success OUT
    IF @success <> 1
      BEGIN

        EXEC sp_OAGetProperty @ws, 'ReadFrameFailReason', @iTmp0 OUT
        PRINT 'ReadFrame fail reason = ' + @iTmp0
        EXEC sp_OAGetProperty @ws, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @ws
        EXEC @hr = sp_OADestroy @rest
        RETURN
      END

    -- Should receive the "Close" opcode.

    EXEC sp_OAGetProperty @ws, 'FrameOpcode', @sTmp0 OUT
    PRINT 'Received opcode: ' + @sTmp0
    -- Should be the same status code we sent (1000)

    EXEC sp_OAGetProperty @ws, 'CloseStatusCode', @iTmp0 OUT
    PRINT 'Received close status code: ' + @iTmp0
    -- The server may echo the close reason.  If not, this will be empty.

    EXEC sp_OAGetProperty @ws, 'CloseReason', @sTmp0 OUT
    PRINT 'Echoed close reason: ' + @sTmp0


    PRINT 'Success.'

    EXEC @hr = sp_OADestroy @ws
    EXEC @hr = sp_OADestroy @rest


END
GO