(Xojo Plugin) Send and Receive WebSocket Messages

This example how to send and receive websocket messages.

A WebSocket message can be composed of one or more frames. The simple case is where a single frame is both the first and last frame in a message. This is the case where the 1st frame in the message has the "final frame" bit set.

This example demonstrates sending and receiving multi-frame messages.

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.

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// 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.
Dim success As Boolean
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 demonstrates sending and receiving a multi-frame message.

// The websocket message will be composed of three text lines, each frame will contain a single line.

// Send the 1st frame in the message.
Dim finalFrame As Boolean
finalFrame = False
success = ws.SendFrame("This is the 1st frame" + EndOfLine.Windows,finalFrame)
If (success <> True) Then
    System.DebugLog(ws.LastErrorText)
    Return
End If

// Send the 2nd frame in the message.
success = ws.SendFrame("This is the 2nd frame" + EndOfLine.Windows,finalFrame)
If (success <> True) Then
    System.DebugLog(ws.LastErrorText)
    Return
End If

// Send the 3rd and final frame in the message.
finalFrame = True
success = ws.SendFrame("This is the 3rd frame" + EndOfLine.Windows,finalFrame)
If (success <> True) Then
    System.DebugLog(ws.LastErrorText)
    Return
End If

// Read an incoming frames until we receive the final frame.
// Note: It may be that the echo server (websockets.chilkat.io) responds with 
// the full message in a single final frame.
Dim receivedFinalFrame As Boolean
receivedFinalFrame = False
While receivedFinalFrame = False

    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

// Return the message accumulated in the above calls to ReadFrame.
Dim receivedMsg As String
receivedMsg = ws.GetFrameData()
System.DebugLog("Received: " + receivedMsg)

// 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.")