Visual FoxPro

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.

Visual FoxPro

LOCAL lnSuccess
LOCAL loWs
LOCAL loRest
LOCAL lcResponseBodyIgnored
LOCAL loJpgData
LOCAL lnFinalFrame
LOCAL lnReceivedFinalFrame
LOCAL loJpgReceivedData

lnSuccess = 0

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

loWs = 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.

loRest = 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.
lnSuccess = loRest.Connect("websockets.chilkat.io",80,0,0)
loWs.UseConnection(loRest)
loWs.AddClientHeaders()
lcResponseBodyIgnored = loRest.FullRequestNoBody("GET","/wsChilkatEcho.ashx")
lnSuccess = loWs.ValidateServerHandshake()
IF (lnSuccess <> 1) THEN
    ? loWs.LastErrorText
    RELEASE loWs
    RELEASE loRest
    CANCEL
ENDIF

* This example sends a small JPG file (about 7KB) in a websocket frame.
loJpgData = CreateObject('Chilkat.BinData')
lnSuccess = loJpgData.LoadFile("qa_data/jpg/starfish.jpg")

? "Number of bytes to send = " + STR(loJpgData.NumBytes)

* Send a frame containing the JPG image data.
* This will be the first and final frame, and therefore this constitutes the entire message.
lnFinalFrame = 1
lnSuccess = loWs.SendFrameBd(loJpgData,lnFinalFrame)
IF (lnSuccess <> 1) THEN
    ? loWs.LastErrorText
    RELEASE loWs
    RELEASE loRest
    RELEASE loJpgData
    CANCEL
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.
lnReceivedFinalFrame = 0
DO WHILE lnReceivedFinalFrame = 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.
    lnSuccess = loWs.ReadFrame()
    IF (lnSuccess <> 1) THEN
        ? "Failed to receive a frame"
        ? "ReadFrame fail reason = " + STR(loWs.ReadFrameFailReason)
        ? loWs.LastErrorText
        RELEASE loWs
        RELEASE loRest
        RELEASE loJpgData
        CANCEL
    ENDIF

    lnReceivedFinalFrame = loWs.FinalFrame

    * Show the opcode and final frame bit for the frame just received:
    ? "Frame opcode: " + loWs.FrameOpcode
    ? "Final frame: " + STR(lnReceivedFinalFrame)
ENDDO

* Get the accumulated received data.
loJpgReceivedData = CreateObject('Chilkat.BinData')
loWs.GetFrameDataBd(loJpgReceivedData)
? "Received " + STR(loJpgReceivedData.NumBytes) + " bytes"

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

* Close the websocket connection.
lnSuccess = loWs.SendClose(1,1000,"Closing this websocket.")
IF (lnSuccess <> 1) THEN
    ? loWs.LastErrorText
    RELEASE loWs
    RELEASE loRest
    RELEASE loJpgData
    RELEASE loJpgReceivedData
    CANCEL
ENDIF

* Read the Close response.
lnSuccess = loWs.ReadFrame()
IF (lnSuccess <> 1) THEN
    ? "ReadFrame fail reason = " + STR(loWs.ReadFrameFailReason)
    ? loWs.LastErrorText
    RELEASE loWs
    RELEASE loRest
    RELEASE loJpgData
    RELEASE loJpgReceivedData
    CANCEL
ENDIF

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

? "Success."

RELEASE loWs
RELEASE loRest
RELEASE loJpgData
RELEASE loJpgReceivedData