Lianja Requires Chilkat v11.0.0+
Lianja
Firebase Receive Server-Sent Events (text/event-stream)
See more Firebase Examples
Demonstrates how to start receiving server-sent events and update your JSON database with each event.Chilkat Lianja Downloads
llSuccess = .F.
// Demonstrates how to begin receiving server-sent events, and to update
// your JSON database for each event.
// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.
// This example assumes a JWT authentication token, if required, has been previously obtained.
// See Get Firebase Access Token from JSON Service Account Private Key for sample code.
// Load the previously obtained Firebase access token into a string.
loFac = createobject("CkFileAccess")
lcAccessToken = loFac.ReadEntireTextFile("qa_data/tokens/firebaseToken.txt","utf-8")
if (loFac.LastMethodSuccess = .F.) then
? loFac.LastErrorText
release loFac
return
endif
loRest = createobject("CkRest")
// Make the initial connection (without sending a request yet).
// Once connected, any number of requests may be sent. It is not necessary to explicitly
// call Connect before each request.
llSuccess = loRest.Connect("chilkat.firebaseio.com",443,.T.,.T.)
if (llSuccess = .F.) then
? loRest.LastErrorText
release loFac
release loRest
return
endif
loAuthGoogle = createobject("CkAuthGoogle")
loAuthGoogle.AccessToken = lcAccessToken
loRest.SetAuthGoogle(loAuthGoogle)
loRest.AddHeader("Accept","text/event-stream")
loRest.AddHeader("Cache-Control","no-cache")
lcResponseBody = loRest.FullRequestNoBody("GET","/.json")
// A 307 redirect response is expected.
if (loRest.ResponseStatusCode <> 307) then
? "Unexpected response code: " + str(loRest.ResponseStatusCode)
? lcResponseBody
? "Failed."
release loFac
release loRest
release loAuthGoogle
return
endif
// Get the redirect URL
lcUrlStr = loRest.LastRedirectUrl
loUrl = createobject("CkUrl")
loUrl.ParseUrl(lcUrlStr)
? "redirect URL domain: " + loUrl.Host
? "redirect URL path: " + loUrl.Path
? "redirect URL query params: " + loUrl.Query
? "redirect URL path with query params: " + loUrl.PathWithQueryParams
// Our text/event-stream will be obtained from the redirect URL...
loRest2 = createobject("CkRest")
llSuccess = loRest2.Connect(loUrl.Host,443,.T.,.T.)
if (llSuccess <> .T.) then
? loRest2.LastErrorText
release loFac
release loRest
release loAuthGoogle
release loUrl
release loRest2
return
endif
loRest2.AddHeader("Accept","text/event-stream")
loRest2.AddHeader("Cache-Control","no-cache")
// Add the redirect query params to the request
loRest2.AddQueryParams(loUrl.Query)
// In our case, we don't actually need the auth query param,
// so remove it.
loRest2.RemoveQueryParam("auth")
// Send the request. (We are only sending the request here.
// We are not yet getting the response because the response
// will be a text/event-stream.)
llSuccess = loRest2.SendReqNoBody("GET",loUrl.Path)
if (llSuccess <> .T.) then
? loRest2.LastErrorText
release loFac
release loRest
release loAuthGoogle
release loUrl
release loRest2
return
endif
// Read the response header.
// We want to first get the response header to see if it's a successful
// response status code. If not, then the response will not be a text/event-stream
// and we should read the response body normally.
lnResponseStatusCode = loRest2.ReadResponseHeader()
if (lnResponseStatusCode < 0) then
? loRest2.LastErrorText
release loFac
release loRest
release loAuthGoogle
release loUrl
release loRest2
return
endif
// If successful, a 200 response code is expected.
// If the reponse code is not 200, then read the response body and fail..
if (lnResponseStatusCode <> 200) then
? "Response Code: " + str(lnResponseStatusCode)
? "Response Status Text: " + loRest2.ResponseStatusText
? "Response Header: " + loRest2.ResponseHeader
lcResponseBody = loRest2.ReadRespBodyString()
if (loRest2.LastMethodSuccess = .T.) then
? "Error Response Body: " + lcResponseBody
endif
? "Failed."
release loFac
release loRest
release loAuthGoogle
release loUrl
release loRest2
return
endif
// For this example, our JSON database will be empty at the beginning.
// The incoming events (put and patch) will be applied to this database.
loJsonDb = createobject("CkJsonObject")
// Make sure to set the JSON path delimiter to "/". The default is "." and this
// is not compatible with Firebase paths.
loJsonDb.DelimiterChar = "/"
// At this point, we've received the response header. Now it's time to begin
// receiving the event stream. We'll start a background thread to read the
// stream. (Our main application (foreground) thread can cancel it at any time.)
// While receiving in the background thread, our foreground thread can read the stream
// as it desires..
loEventStream = createobject("CkStream")
// This sse object will be used as a helper to parse the server-sent event stream.
loSse = createobject("CkServerSentEvent")
loTask = loRest2.ReadRespBodyStreamAsync(loEventStream,.T.)
loTask.Run()
// For this example, we'll just read a few events, and then cancel the
// async task.
lnCount = 0
do while (lnCount < 3) and (loTask.Finished = .F.)
// Get the next event, which is a series of text lines ending with
// a blank line.
// Note: This method blocks the calling thread until a message arrives.
// a program might instead periodically check the availability of
// data via the stream's DataAvailable property, and then do the read.
// An alternative to writing a while loop to read the event stream
// would be to setup some sort of timer event in your program (using whatever timer functionality
// is provided in a programming language/environment), to periodically check the eventStream's
// DataAvailable property and consume the incoming event.
lcEventStr = loEventStream.ReadUntilMatch(Chr(13) + Chr(10) + Chr(13) + Chr(10))
if (loEventStream.LastMethodSuccess <> .T.) then
? loEventStream.LastErrorText
// Force the loop to exit by setting the count to a high number.
lnCount = 99999
else
? "Event: [" + lcEventStr + "]"
// We have an event. Let's update our local copy of the JSON database.
llSuccess = loSse.LoadEvent(lcEventStr)
if (llSuccess <> .T.) then
? "Failed to load sse event: " + lcEventStr
else
// Now we can easily access the event name and data, and apply it to our JSON database:
llSuccess = loJsonDb.FirebaseApplyEvent(loSse.EventName,loSse.Data)
if (llSuccess <> .T.) then
? "Failed to apply event: " + loSse.EventName + ": " + loSse.Data
else
? "Successfully applied event: " + loSse.EventName + ": " + loSse.Data
endif
endif
endif
lnCount = lnCount + 1
enddo
// Make sure the background task is cancelled if still running.
loTask.Cancel()
release loTask
// Examine the JSON database after applying events..
loJsonDb.EmitCompact = .F.
? "----"
? loJsonDb.Emit()
release loFac
release loRest
release loAuthGoogle
release loUrl
release loRest2
release loJsonDb
release loEventStream
release loSse