Node.js

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.

Node.js

NODEJS_PRELUDE

function chilkatExample() {

    var success = false;

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

    var ws = 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.

    var rest = 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();
    var responseBodyIgnored = rest.FullRequestNoBody("GET","/wsChilkatEcho.ashx");
    success = ws.ValidateServerHandshake();
    if (success !== true) {
        console.log(ws.LastErrorText);
        return;
    }

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

    console.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.
    var finalFrame = true;
    success = ws.SendFrameBd(jpgData,finalFrame);
    if (success !== true) {
        console.log(ws.LastErrorText);
        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.
    var 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) {
            console.log("Failed to receive a frame");
            console.log("ReadFrame fail reason = " + ws.ReadFrameFailReason);
            console.log(ws.LastErrorText);
            return;
        }

        receivedFinalFrame = ws.FinalFrame;

        //  Show the opcode and final frame bit for the frame just received:
        console.log("Frame opcode: " + ws.FrameOpcode);
        console.log("Final frame: " + receivedFinalFrame);
    }

    //  Get the accumulated received data.
    var jpgReceivedData = new chilkat.BinData();
    ws.GetFrameDataBd(jpgReceivedData);
    console.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) {
        console.log(ws.LastErrorText);
        return;
    }

    //  Read the Close response.
    success = ws.ReadFrame();
    if (success !== true) {
        console.log("ReadFrame fail reason = " + ws.ReadFrameFailReason);
        console.log(ws.LastErrorText);
        return;
    }

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

    console.log("Success.");

}

chilkatExample();