Xbase++

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.

Xbase++

LOCAL nSuccess
LOCAL oWs
LOCAL oRest
LOCAL cResponseBodyIgnored
LOCAL nFinalFrame
LOCAL nReceivedFinalFrame
LOCAL cReceivedMsg

nSuccess := 0

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

oWs := CreateObject("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.

oRest := CreateObject("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.
nSuccess := oRest:Connect("websockets.chilkat.io", 80, 0, 0)
oWs:UseConnection(oRest)
oWs:AddClientHeaders()
cResponseBodyIgnored := oRest:FullRequestNoBody("GET", "/wsChilkatEcho.ashx")
nSuccess := oWs:ValidateServerHandshake()
IF (nSuccess != 1)
    ? oWs:LastErrorText
    oWs:destroy()
    oRest:destroy()
    RETURN
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.
nFinalFrame := 0
nSuccess := oWs:SendFrame("This is the 1st frame" + Chr(13) + Chr(10), nFinalFrame)
IF (nSuccess != 1)
    ? oWs:LastErrorText
    oWs:destroy()
    oRest:destroy()
    RETURN
ENDIF

//  Send the 2nd frame in the message.
nSuccess := oWs:SendFrame("This is the 2nd frame" + Chr(13) + Chr(10), nFinalFrame)
IF (nSuccess != 1)
    ? oWs:LastErrorText
    oWs:destroy()
    oRest:destroy()
    RETURN
ENDIF

//  Send the 3rd and final frame in the message.
nFinalFrame := 1
nSuccess := oWs:SendFrame("This is the 3rd frame" + Chr(13) + Chr(10), nFinalFrame)
IF (nSuccess != 1)
    ? oWs:LastErrorText
    oWs:destroy()
    oRest:destroy()
    RETURN
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.
nReceivedFinalFrame := 0
DO WHILE nReceivedFinalFrame == 0

    nSuccess := oWs:ReadFrame()
    IF (nSuccess != 1)
        ? "Failed to receive a frame"
        ? "ReadFrame fail reason = " + Str(oWs:ReadFrameFailReason)
        ? oWs:LastErrorText
        oWs:destroy()
        oRest:destroy()
        RETURN
    ENDIF

    nReceivedFinalFrame := oWs:FinalFrame

    //  Show the opcode and final frame bit for the frame just received:
    ? "Frame opcode: " + oWs:FrameOpcode
    ? "Final frame: " + Str(nReceivedFinalFrame)
ENDDO

//  Return the message accumulated in the above calls to ReadFrame.
cReceivedMsg := oWs:GetFrameData()
? "Received: " + cReceivedMsg

//  Close the websocket connection.
nSuccess := oWs:SendClose(1, 1000, "Closing this websocket.")
IF (nSuccess != 1)
    ? oWs:LastErrorText
    oWs:destroy()
    oRest:destroy()
    RETURN
ENDIF

//  Read the Close response.
nSuccess := oWs:ReadFrame()
IF (nSuccess != 1)
    ? "ReadFrame fail reason = " + Str(oWs:ReadFrameFailReason)
    ? oWs:LastErrorText
    oWs:destroy()
    oRest:destroy()
    RETURN
ENDIF

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

? "Success."

oWs:destroy()
oRest:destroy()