B4X

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.

B4X

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 ChilkatWebSocket
ws.Initialize("ws")

'  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 ChilkatRest
rest.Initialize("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
    Log(ws.LastErrorText)
    Return
End If


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

Log("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
    Log(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 = False
Do 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
        Log("Failed to receive a frame")
        Log("ReadFrame fail reason = " & ws.ReadFrameFailReason)
        Log(ws.LastErrorText)
        Return
    End If


    receivedFinalFrame = ws.FinalFrame

    '  Show the opcode and final frame bit for the frame just received:
    Log("Frame opcode: " & ws.FrameOpcode)
    Log("Final frame: " & receivedFinalFrame)
Loop

'  Get the accumulated received data.
Dim jpgReceivedData As ChilkatBinData
jpgReceivedData.Initialize
ws.GetFrameDataBd(jpgReceivedData)
Log("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
    Log(ws.LastErrorText)
    Return
End If


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


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

Log("Success.")