Node.js

Send and Receive WebSocket Messages

See more WebSocket Examples

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.

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 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.
    var finalFrame = false;
    success = ws.SendFrame("This is the 1st frame\r\n",finalFrame);
    if (success !== true) {
        console.log(ws.LastErrorText);
        return;
    }

    //  Send the 2nd frame in the message.
    success = ws.SendFrame("This is the 2nd frame\r\n",finalFrame);
    if (success !== true) {
        console.log(ws.LastErrorText);
        return;
    }

    //  Send the 3rd and final frame in the message.
    finalFrame = true;
    success = ws.SendFrame("This is the 3rd frame\r\n",finalFrame);
    if (success !== true) {
        console.log(ws.LastErrorText);
        return;
    }

    //  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.
    var receivedFinalFrame = false;
    while (receivedFinalFrame == false) {

        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);
    }

    //  Return the message accumulated in the above calls to ReadFrame.
    var receivedMsg = ws.GetFrameData();
    console.log("Received: " + receivedMsg);

    //  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();