PureBasic

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.

PureBasic

IncludeFile "CkWebSocket.pb"
IncludeFile "CkRest.pb"

Procedure ChilkatExample()

    success.i = 0

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

    ws.i = CkWebSocket::ckCreate()
    If ws.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    ; 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.i = CkRest::ckCreate()
    If rest.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    ; 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 = CkRest::ckConnect(rest,"websockets.chilkat.io",80,0,0)
    CkWebSocket::ckUseConnection(ws,rest)
    CkWebSocket::ckAddClientHeaders(ws)
    responseBodyIgnored.s = CkRest::ckFullRequestNoBody(rest,"GET","/wsChilkatEcho.ashx")
    success = CkWebSocket::ckValidateServerHandshake(ws)
    If success <> 1
        Debug CkWebSocket::ckLastErrorText(ws)
        CkWebSocket::ckDispose(ws)
        CkRest::ckDispose(rest)
        ProcedureReturn
    EndIf

    ; 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.
    finalFrame.i = 0
    success = CkWebSocket::ckSendFrame(ws,"This is the 1st frame" + Chr(13) + Chr(10),finalFrame)
    If success <> 1
        Debug CkWebSocket::ckLastErrorText(ws)
        CkWebSocket::ckDispose(ws)
        CkRest::ckDispose(rest)
        ProcedureReturn
    EndIf

    ; Send the 2nd frame in the message.
    success = CkWebSocket::ckSendFrame(ws,"This is the 2nd frame" + Chr(13) + Chr(10),finalFrame)
    If success <> 1
        Debug CkWebSocket::ckLastErrorText(ws)
        CkWebSocket::ckDispose(ws)
        CkRest::ckDispose(rest)
        ProcedureReturn
    EndIf

    ; Send the 3rd and final frame in the message.
    finalFrame = 1
    success = CkWebSocket::ckSendFrame(ws,"This is the 3rd frame" + Chr(13) + Chr(10),finalFrame)
    If success <> 1
        Debug CkWebSocket::ckLastErrorText(ws)
        CkWebSocket::ckDispose(ws)
        CkRest::ckDispose(rest)
        ProcedureReturn
    EndIf

    ; 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.
    receivedFinalFrame.i = 0
    While receivedFinalFrame = 0

        success = CkWebSocket::ckReadFrame(ws)
        If success <> 1
            Debug "Failed to receive a frame"
            Debug "ReadFrame fail reason = " + Str(CkWebSocket::ckReadFrameFailReason(ws))
            Debug CkWebSocket::ckLastErrorText(ws)
            CkWebSocket::ckDispose(ws)
            CkRest::ckDispose(rest)
            ProcedureReturn
        EndIf

        receivedFinalFrame = CkWebSocket::ckFinalFrame(ws)

        ; Show the opcode and final frame bit for the frame just received:
        Debug "Frame opcode: " + CkWebSocket::ckFrameOpcode(ws)
        Debug "Final frame: " + Str(receivedFinalFrame)
    Wend

    ; Return the message accumulated in the above calls to ReadFrame.
    receivedMsg.s = CkWebSocket::ckGetFrameData(ws)
    Debug "Received: " + receivedMsg

    ; Close the websocket connection.
    success = CkWebSocket::ckSendClose(ws,1,1000,"Closing this websocket.")
    If success <> 1
        Debug CkWebSocket::ckLastErrorText(ws)
        CkWebSocket::ckDispose(ws)
        CkRest::ckDispose(rest)
        ProcedureReturn
    EndIf

    ; Read the Close response.
    success = CkWebSocket::ckReadFrame(ws)
    If success <> 1
        Debug "ReadFrame fail reason = " + Str(CkWebSocket::ckReadFrameFailReason(ws))
        Debug CkWebSocket::ckLastErrorText(ws)
        CkWebSocket::ckDispose(ws)
        CkRest::ckDispose(rest)
        ProcedureReturn
    EndIf

    ; Should receive the "Close" opcode.
    Debug "Received opcode: " + CkWebSocket::ckFrameOpcode(ws)
    ; Should be the same status code we sent (1000)
    Debug "Received close status code: " + Str(CkWebSocket::ckCloseStatusCode(ws))
    ; The server may echo the close reason.  If not, this will be empty.
    Debug "Echoed close reason: " + CkWebSocket::ckCloseReason(ws)

    Debug "Success."


    CkWebSocket::ckDispose(ws)
    CkRest::ckDispose(rest)


    ProcedureReturn
EndProcedure