Lianja

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.

Lianja

llSuccess = .F.

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

loWs = createobject("CkWebSocket")

// 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.

loRest = createobject("CkRest")
// 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.
llSuccess = loRest.Connect("websockets.chilkat.io",80,.F.,.F.)
loWs.UseConnection(loRest)
loWs.AddClientHeaders()
lcResponseBodyIgnored = loRest.FullRequestNoBody("GET","/wsChilkatEcho.ashx")
llSuccess = loWs.ValidateServerHandshake()
if (llSuccess <> .T.) then
    ? loWs.LastErrorText
    release loWs
    release loRest
    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.
llFinalFrame = .F.
llSuccess = loWs.SendFrame("This is the 1st frame" + Chr(13) + Chr(10),llFinalFrame)
if (llSuccess <> .T.) then
    ? loWs.LastErrorText
    release loWs
    release loRest
    return
endif

// Send the 2nd frame in the message.
llSuccess = loWs.SendFrame("This is the 2nd frame" + Chr(13) + Chr(10),llFinalFrame)
if (llSuccess <> .T.) then
    ? loWs.LastErrorText
    release loWs
    release loRest
    return
endif

// Send the 3rd and final frame in the message.
llFinalFrame = .T.
llSuccess = loWs.SendFrame("This is the 3rd frame" + Chr(13) + Chr(10),llFinalFrame)
if (llSuccess <> .T.) then
    ? loWs.LastErrorText
    release loWs
    release loRest
    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.
llReceivedFinalFrame = .F.
do while llReceivedFinalFrame = .F.

    llSuccess = loWs.ReadFrame()
    if (llSuccess <> .T.) then
        ? "Failed to receive a frame"
        ? "ReadFrame fail reason = " + str(loWs.ReadFrameFailReason)
        ? loWs.LastErrorText
        release loWs
        release loRest
        return
    endif

    llReceivedFinalFrame = loWs.FinalFrame

    // Show the opcode and final frame bit for the frame just received:
    ? "Frame opcode: " + loWs.FrameOpcode
    ? "Final frame: " + str(llReceivedFinalFrame)
enddo

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

// Close the websocket connection.
llSuccess = loWs.SendClose(.T.,1000,"Closing this websocket.")
if (llSuccess <> .T.) then
    ? loWs.LastErrorText
    release loWs
    release loRest
    return
endif

// Read the Close response.
llSuccess = loWs.ReadFrame()
if (llSuccess <> .T.) then
    ? "ReadFrame fail reason = " + str(loWs.ReadFrameFailReason)
    ? loWs.LastErrorText
    release loWs
    release loRest
    return
endif

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

? "Success."


release loWs
release loRest