VB.NET

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.

VB.NET

Dim success As Boolean = 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)
ws.UseConnection(rest)
ws.AddClientHeaders()
Dim responseBodyIgnored As String = rest.FullRequestNoBody("GET","/wsChilkatEcho.ashx")
success = ws.ValidateServerHandshake()
If (success <> True) Then
    Debug.WriteLine(ws.LastErrorText)
    Exit Sub
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")

Debug.WriteLine("Number of bytes to send = " & 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 = True
success = ws.SendFrameBd(jpgData,finalFrame)
If (success <> True) Then
    Debug.WriteLine(ws.LastErrorText)
    Exit Sub
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 = 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
        Debug.WriteLine("Failed to receive a frame")
        Debug.WriteLine("ReadFrame fail reason = " & ws.ReadFrameFailReason)
        Debug.WriteLine(ws.LastErrorText)
        Exit Sub
    End If


    receivedFinalFrame = ws.FinalFrame

    ' Show the opcode and final frame bit for the frame just received:
    Debug.WriteLine("Frame opcode: " & ws.FrameOpcode)
    Debug.WriteLine("Final frame: " & receivedFinalFrame)
End While

' Get the accumulated received data.
Dim jpgReceivedData As New Chilkat.BinData
ws.GetFrameDataBd(jpgReceivedData)
Debug.WriteLine("Received " & jpgReceivedData.NumBytes & " bytes")

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

' Close the websocket connection.
success = ws.SendClose(True,1000,"Closing this websocket.")
If (success <> True) Then
    Debug.WriteLine(ws.LastErrorText)
    Exit Sub
End If


' Read the Close response.
success = ws.ReadFrame()
If (success <> True) Then
    Debug.WriteLine("ReadFrame fail reason = " & ws.ReadFrameFailReason)
    Debug.WriteLine(ws.LastErrorText)
    Exit Sub
End If


' Should receive the "Close" opcode.
Debug.WriteLine("Received opcode: " & ws.FrameOpcode)
' Should be the same status code we sent (1000)
Debug.WriteLine("Received close status code: " & ws.CloseStatusCode)
' The server may echo the close reason.  If not, this will be empty.
Debug.WriteLine("Echoed close reason: " & ws.CloseReason)

Debug.WriteLine("Success.")