(Visual FoxPro) Read Bitfinex WebSocket Ticker Channel

Subscribes to the public Bitfinex websocket ticker channel and receives ticker updates.

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

LOCAL loWs
LOCAL loRest
LOCAL lnSuccess
LOCAL lcResponseBody
LOCAL loJson
LOCAL lnFinalFrame
LOCAL lnReceivedFinalFrame
LOCAL lnNumUpdatesReceived
LOCAL lcReceivedText

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

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.WebSocket')
loWs = 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.

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.Rest')
loRest = CreateObject('Chilkat.Rest')

* Connect to api.bitfinex.com
lnSuccess = loRest.Connect("api.bitfinex.com",443,1,0)
loWs.UseConnection(loRest)
loWs.AddClientHeaders()

lcResponseBody = loRest.FullRequestNoBody("GET","/ws")
lnSuccess = loWs.ValidateServerHandshake()
IF (lnSuccess <> 1) THEN
    ? loWs.LastErrorText
    ? lcResponseBody
    ? loRest.ResponseHeader
    RELEASE loWs
    RELEASE loRest
    CANCEL
ENDIF

* After connecting, the bitfinex websocket server will send
* an info message that contains the actual version of the websocket stream.
* Receive that message..
lnSuccess = loWs.ReadFrame()
IF (lnSuccess <> 1) THEN
    ? "Failed to receive a frame"
    ? "ReadFrame fail reason = " + STR(loWs.ReadFrameFailReason)
    ? loWs.LastErrorText
    RELEASE loWs
    RELEASE loRest
    CANCEL
ENDIF

* We should get this:
* {"event":"info","version":1.1,"platform":{"status":1}}
? loWs.GetFrameData()

* Subscribe to the public ticker feed.
* See https://docs.bitfinex.com/docs for more information.
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.JsonObject')
loJson = CreateObject('Chilkat.JsonObject')
loJson.AppendString("event","subscribe")
loJson.AppendString("channel","ticker")
loJson.AppendString("pair","BTCUSD")

lnFinalFrame = 1
lnSuccess = loWs.SendFrame(loJson.Emit(),lnFinalFrame)

* Read the response.
lnSuccess = loWs.ReadFrame()
IF (lnSuccess <> 1) THEN
    ? "Failed to receive a frame"
    ? "ReadFrame fail reason = " + STR(loWs.ReadFrameFailReason)
    ? loWs.LastErrorText
    RELEASE loWs
    RELEASE loRest
    RELEASE loJson
    CANCEL
ENDIF

* Examine the response
* We should get this:
* {"event":"subscribed","channel":"ticker","chanId":2751,"pair":"BTCUSD"}
? loWs.GetFrameData()

* Begin reading the ticker feed.
* We'll just read the 1st 5 updates and then exit..
lnReceivedFinalFrame = 0
lnNumUpdatesReceived = 0
DO WHILE lnNumUpdatesReceived < 5

    lnSuccess = loWs.ReadFrame()
    IF (lnSuccess <> 1) THEN
        ? "Failed to receive a frame"
        ? "ReadFrame fail reason = " + STR(loWs.ReadFrameFailReason)
        ? loWs.LastErrorText
        RELEASE loWs
        RELEASE loRest
        RELEASE loJson
        CANCEL
    ENDIF

    * The responses we desire are in Text frames, where the opcode = 1.
    IF (loWs.FrameOpcodeInt = 1) THEN
        lcReceivedText = loWs.GetFrameData()
        ? lcReceivedText
        * Should receive a line of text such as this:
        * [2751,7349,36.34269559,7349.1,41.01777063,-116.2,-0.0156,7349.1,22188.26055319,7560,7270.5]
        lnNumUpdatesReceived = lnNumUpdatesReceived + 1
    ENDIF

ENDDO

* Close the websocket connection.
lnSuccess = loWs.SendClose(1,1000,"Closing this websocket.")
IF (lnSuccess <> 1) THEN
    ? loWs.LastErrorText
    RELEASE loWs
    RELEASE loRest
    RELEASE loJson
    CANCEL
ENDIF

* Read the Close response.
lnSuccess = loWs.ReadFrame()
IF (lnSuccess <> 1) THEN
    ? "ReadFrame fail reason = " + STR(loWs.ReadFrameFailReason)
    ? loWs.LastErrorText
    RELEASE loWs
    RELEASE loRest
    RELEASE loJson
    CANCEL
ENDIF

? "Success."

RELEASE loWs
RELEASE loRest
RELEASE loJson