(MFC) 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.

Chilkat C/C++ Library Downloads MS Visual C/C++ Libs

See Also: Using MFC CString in Chilkat

#include <CkWebSocket.h>
#include <CkRest.h>

void ChilkatSample(void)
    {
    CkString strOut;

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

    CkWebSocket 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.

    CkRest 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.
    bool success = rest.Connect("websockets.chilkat.io",80,false,false);
    ws.UseConnection(rest);
    ws.AddClientHeaders();
    const char *responseBodyIgnored = rest.fullRequestNoBody("GET","/wsChilkatEcho.ashx");
    success = ws.ValidateServerHandshake();
    if (success != true) {
        strOut.append(ws.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        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.
    bool finalFrame = false;
    success = ws.SendFrame("This is the 1st frame\r\n",finalFrame);
    if (success != true) {
        strOut.append(ws.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // Send the 2nd frame in the message.
    success = ws.SendFrame("This is the 2nd frame\r\n",finalFrame);
    if (success != true) {
        strOut.append(ws.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        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) {
        strOut.append(ws.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        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.
    bool receivedFinalFrame = false;
    while (receivedFinalFrame == false) {

        success = ws.ReadFrame();
        if (success != true) {
            strOut.append("Failed to receive a frame");
            strOut.append("\r\n");
            strOut.append("ReadFrame fail reason = ");
            strOut.appendInt(ws.get_ReadFrameFailReason());
            strOut.append("\r\n");
            strOut.append(ws.lastErrorText());
            strOut.append("\r\n");
            SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
            return;
        }

        receivedFinalFrame = ws.get_FinalFrame();

        // Show the opcode and final frame bit for the frame just received:
        strOut.append("Frame opcode: ");
        strOut.append(ws.frameOpcode());
        strOut.append("\r\n");
        strOut.append("Final frame: ");
        strOut.appendInt(receivedFinalFrame);
        strOut.append("\r\n");
    }

    // Return the message accumulated in the above calls to ReadFrame.
    const char *receivedMsg = ws.getFrameData();
    strOut.append("Received: ");
    strOut.append(receivedMsg);
    strOut.append("\r\n");

    // Close the websocket connection.
    success = ws.SendClose(true,1000,"Closing this websocket.");
    if (success != true) {
        strOut.append(ws.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // Read the Close response.
    success = ws.ReadFrame();
    if (success != true) {
        strOut.append("ReadFrame fail reason = ");
        strOut.appendInt(ws.get_ReadFrameFailReason());
        strOut.append("\r\n");
        strOut.append(ws.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // Should receive the "Close" opcode.
    strOut.append("Received opcode: ");
    strOut.append(ws.frameOpcode());
    strOut.append("\r\n");
    // Should be the same status code we sent (1000)
    strOut.append("Received close status code: ");
    strOut.appendInt(ws.get_CloseStatusCode());
    strOut.append("\r\n");
    // The server may echo the close reason.  If not, this will be empty.
    strOut.append("Echoed close reason: ");
    strOut.append(ws.closeReason());
    strOut.append("\r\n");

    strOut.append("Success.");
    strOut.append("\r\n");


    SetDlgItemText(IDC_EDIT1,strOut.getUnicode());

    }