Lianja

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.

Lianja

llSuccess = .F.

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

loWs = createobject("CkWebSocket")

// 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("CkRest")
// 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.
llSuccess = loRest.Connect("websockets.chilkat.io",80,.F.,.F.)
loWs.UseConnection(loRest)
loWs.AddClientHeaders()
lcResponseBodyIgnored = loRest.FullRequestNoBody("GET","/wsChilkatEcho.ashx")
llSuccess = loWs.ValidateServerHandshake()
if (llSuccess <> .T.) then
    ? loWs.LastErrorText
    release loWs
    release loRest
    return
endif

// This example sends a small JPG file (about 7KB) in a websocket frame.
loJpgData = createobject("CkBinData")
llSuccess = 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.
llFinalFrame = .T.
llSuccess = loWs.SendFrameBd(loJpgData,llFinalFrame)
if (llSuccess <> .T.) then
    ? loWs.LastErrorText
    release loWs
    release loRest
    release loJpgData
    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.
llReceivedFinalFrame = .F.
do while llReceivedFinalFrame = .F.

    // 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.
    llSuccess = loWs.ReadFrame()
    if (llSuccess <> .T.) then
        ? "Failed to receive a frame"
        ? "ReadFrame fail reason = " + str(loWs.ReadFrameFailReason)
        ? loWs.LastErrorText
        release loWs
        release loRest
        release loJpgData
        return
    endif

    llReceivedFinalFrame = loWs.FinalFrame

    // Show the opcode and final frame bit for the frame just received:
    ? "Frame opcode: " + loWs.FrameOpcode
    ? "Final frame: " + str(llReceivedFinalFrame)
enddo

// Get the accumulated received data.
loJpgReceivedData = createobject("CkBinData")
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.
llSuccess = loWs.SendClose(.T.,1000,"Closing this websocket.")
if (llSuccess <> .T.) then
    ? loWs.LastErrorText
    release loWs
    release loRest
    release loJpgData
    release loJpgReceivedData
    return
endif

// Read the Close response.
llSuccess = loWs.ReadFrame()
if (llSuccess <> .T.) then
    ? "ReadFrame fail reason = " + str(loWs.ReadFrameFailReason)
    ? loWs.LastErrorText
    release loWs
    release loRest
    release loJpgData
    release loJpgReceivedData
    return
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