Xojo Plugin

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.

Xojo Plugin

Dim success As Boolean
success = False

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

Dim ws As New 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.

Dim rest As New 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.
success = rest.Connect("websockets.chilkat.io",80,False,False)
success = ws.UseConnection(rest)
success = ws.AddClientHeaders()
Dim responseBodyIgnored As String
responseBodyIgnored = rest.FullRequestNoBody("GET","/wsChilkatEcho.ashx")
success = ws.ValidateServerHandshake()
If (success <> True) Then
    System.DebugLog(ws.LastErrorText)
    Return
End If

// This example sends a small JPG file (about 7KB) in a websocket frame.
Dim jpgData As New Chilkat.BinData
success = jpgData.LoadFile("qa_data/jpg/starfish.jpg")

System.DebugLog("Number of bytes to send = " + Str(jpgData.NumBytes))

// Send a frame containing the JPG image data.
// This will be the first and final frame, and therefore this constitutes the entire message.
Dim finalFrame As Boolean
finalFrame = True
success = ws.SendFrameBd(jpgData,finalFrame)
If (success <> True) Then
    System.DebugLog(ws.LastErrorText)
    Return
End If

// 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.
Dim receivedFinalFrame As Boolean
receivedFinalFrame = False
While receivedFinalFrame = False

    // 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.
    success = ws.ReadFrame()
    If (success <> True) Then
        System.DebugLog("Failed to receive a frame")
        System.DebugLog("ReadFrame fail reason = " + Str(ws.ReadFrameFailReason))
        System.DebugLog(ws.LastErrorText)
        Return
    End If

    receivedFinalFrame = ws.FinalFrame

    // Show the opcode and final frame bit for the frame just received:
    System.DebugLog("Frame opcode: " + ws.FrameOpcode)
    System.DebugLog("Final frame: " + Str(receivedFinalFrame))
Wend

// Get the accumulated received data.
Dim jpgReceivedData As New Chilkat.BinData
success = ws.GetFrameDataBd(jpgReceivedData)
System.DebugLog("Received " + Str(jpgReceivedData.NumBytes) + " bytes")

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

// Close the websocket connection.
success = ws.SendClose(True,1000,"Closing this websocket.")
If (success <> True) Then
    System.DebugLog(ws.LastErrorText)
    Return
End If

// Read the Close response.
success = ws.ReadFrame()
If (success <> True) Then
    System.DebugLog("ReadFrame fail reason = " + Str(ws.ReadFrameFailReason))
    System.DebugLog(ws.LastErrorText)
    Return
End If

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

System.DebugLog("Success.")