Xbase++

WebSocket Send/Receive Binary Data

See more WebSocket Examples

Demonstrates how to send and receive binary data on a websocket. This example uses Chilkat's websocket test echo server at ws://websockets.chilkat.io/wsChilkatEcho.ashx

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.

Xbase++

LOCAL nSuccess
LOCAL oWs
LOCAL oRest
LOCAL cResponseBodyIgnored
LOCAL oJpgData
LOCAL nFinalFrame
LOCAL nReceivedFinalFrame
LOCAL oJpgReceivedData

nSuccess := 0

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

oWs := CreateObject("Chilkat.WebSocket")

//  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.

oRest := CreateObject("Chilkat.Rest")
//  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.
nSuccess := oRest:Connect("websockets.chilkat.io", 80, 0, 0)
oWs:UseConnection(oRest)
oWs:AddClientHeaders()
cResponseBodyIgnored := oRest:FullRequestNoBody("GET", "/wsChilkatEcho.ashx")
nSuccess := oWs:ValidateServerHandshake()
IF (nSuccess != 1)
    ? oWs:LastErrorText
    oWs:destroy()
    oRest:destroy()
    RETURN
ENDIF

//  This example sends a small JPG file (about 7KB) in a websocket frame.
oJpgData := CreateObject("Chilkat.BinData")
nSuccess := oJpgData:LoadFile("qa_data/jpg/starfish.jpg")

? "Number of bytes to send = " + Str(oJpgData:NumBytes)

//  Send a frame containing the JPG image data.
//  This will be the first and final frame, and therefore this constitutes the entire message.
nFinalFrame := 1
nSuccess := oWs:SendFrameBd(oJpgData, nFinalFrame)
IF (nSuccess != 1)
    ? oWs:LastErrorText
    oWs:destroy()
    oRest:destroy()
    oJpgData:destroy()
    RETURN
ENDIF

//  Read the echoed binary frame(s).
//  (We sent the JPG file in a single frame, but we may receive the echo in multiple frames, but it will be one message.)
//  Read an incoming frames until we receive the final frame.
nReceivedFinalFrame := 0
DO WHILE nReceivedFinalFrame == 0

    //  The ws object is accumulating the received data internally.  Once we get the final frame, we'll get the 
    //  accumulated data which should constitute the entire JPG.
    nSuccess := oWs:ReadFrame()
    IF (nSuccess != 1)
        ? "Failed to receive a frame"
        ? "ReadFrame fail reason = " + Str(oWs:ReadFrameFailReason)
        ? oWs:LastErrorText
        oWs:destroy()
        oRest:destroy()
        oJpgData:destroy()
        RETURN
    ENDIF

    nReceivedFinalFrame := oWs:FinalFrame

    //  Show the opcode and final frame bit for the frame just received:
    ? "Frame opcode: " + oWs:FrameOpcode
    ? "Final frame: " + Str(nReceivedFinalFrame)
ENDDO

//  Get the accumulated received data.
oJpgReceivedData := CreateObject("Chilkat.BinData")
oWs:GetFrameDataBd(oJpgReceivedData)
? "Received " + Str(oJpgReceivedData:NumBytes) + " bytes"

//  Save the received JPG to a file so we can check it..
oJpgReceivedData:WriteFile("qa_output/starfish_ws.jpg")

//  Close the websocket connection.
nSuccess := oWs:SendClose(1, 1000, "Closing this websocket.")
IF (nSuccess != 1)
    ? oWs:LastErrorText
    oWs:destroy()
    oRest:destroy()
    oJpgData:destroy()
    oJpgReceivedData:destroy()
    RETURN
ENDIF

//  Read the Close response.
nSuccess := oWs:ReadFrame()
IF (nSuccess != 1)
    ? "ReadFrame fail reason = " + Str(oWs:ReadFrameFailReason)
    ? oWs:LastErrorText
    oWs:destroy()
    oRest:destroy()
    oJpgData:destroy()
    oJpgReceivedData:destroy()
    RETURN
ENDIF

//  Should receive the "Close" opcode.
? "Received opcode: " + oWs:FrameOpcode
//  Should be the same status code we sent (1000)
? "Received close status code: " + Str(oWs:CloseStatusCode)
//  The server may echo the close reason.  If not, this will be empty.
? "Echoed close reason: " + oWs:CloseReason

? "Success."

oWs:destroy()
oRest:destroy()
oJpgData:destroy()
oJpgReceivedData:destroy()