Go

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.

Go

    success := false

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

    ws := chilkat.NewWebSocket()

    // 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.

    rest := chilkat.NewRest()
    // 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()
    responseBodyIgnored := rest.FullRequestNoBody("GET","/wsChilkatEcho.ashx")
    success = ws.ValidateServerHandshake()
    if success != true {
        fmt.Println(ws.LastErrorText())
        ws.DisposeWebSocket()
        rest.DisposeRest()
        return
    }

    // This example sends a small JPG file (about 7KB) in a websocket frame.
    jpgData := chilkat.NewBinData()
    success = jpgData.LoadFile("qa_data/jpg/starfish.jpg")

    fmt.Println("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.
    finalFrame := true
    success = ws.SendFrameBd(jpgData,finalFrame)
    if success != true {
        fmt.Println(ws.LastErrorText())
        ws.DisposeWebSocket()
        rest.DisposeRest()
        jpgData.DisposeBinData()
        return
    }

    // 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.
    receivedFinalFrame := false
    for 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 {
            fmt.Println("Failed to receive a frame")
            fmt.Println("ReadFrame fail reason = ", ws.ReadFrameFailReason())
            fmt.Println(ws.LastErrorText())
            ws.DisposeWebSocket()
            rest.DisposeRest()
            jpgData.DisposeBinData()
            return
        }

        receivedFinalFrame = ws.FinalFrame()

        // Show the opcode and final frame bit for the frame just received:
        fmt.Println("Frame opcode: ", ws.FrameOpcode())
        fmt.Println("Final frame: ", receivedFinalFrame)
    }

    // Get the accumulated received data.
    jpgReceivedData := chilkat.NewBinData()
    ws.GetFrameDataBd(jpgReceivedData)
    fmt.Println("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 {
        fmt.Println(ws.LastErrorText())
        ws.DisposeWebSocket()
        rest.DisposeRest()
        jpgData.DisposeBinData()
        jpgReceivedData.DisposeBinData()
        return
    }

    // Read the Close response.
    success = ws.ReadFrame()
    if success != true {
        fmt.Println("ReadFrame fail reason = ", ws.ReadFrameFailReason())
        fmt.Println(ws.LastErrorText())
        ws.DisposeWebSocket()
        rest.DisposeRest()
        jpgData.DisposeBinData()
        jpgReceivedData.DisposeBinData()
        return
    }

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

    fmt.Println("Success.")

    ws.DisposeWebSocket()
    rest.DisposeRest()
    jpgData.DisposeBinData()
    jpgReceivedData.DisposeBinData()