Delphi DLL Requires Chilkat v11.0.0+
Delphi DLL
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 Delphi DLL Downloads
var
success: Boolean;
fac: HCkFileAccess;
accessToken: PWideChar;
rest: HCkRest;
authGoogle: HCkAuthGoogle;
responseBody: PWideChar;
urlStr: PWideChar;
url: HCkUrl;
rest2: HCkRest;
responseStatusCode: Integer;
jsonDb: HCkJsonObject;
eventStream: HCkStream;
sse: HCkServerSentEvent;
task: HCkTask;
count: Integer;
eventStr: PWideChar;
begin
success := False;
// 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.
fac := CkFileAccess_Create();
accessToken := CkFileAccess__readEntireTextFile(fac,'qa_data/tokens/firebaseToken.txt','utf-8');
if (CkFileAccess_getLastMethodSuccess(fac) = False) then
begin
Memo1.Lines.Add(CkFileAccess__lastErrorText(fac));
Exit;
end;
rest := CkRest_Create();
// 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.
success := CkRest_Connect(rest,'chilkat.firebaseio.com',443,True,True);
if (success = False) then
begin
Memo1.Lines.Add(CkRest__lastErrorText(rest));
Exit;
end;
authGoogle := CkAuthGoogle_Create();
CkAuthGoogle_putAccessToken(authGoogle,accessToken);
CkRest_SetAuthGoogle(rest,authGoogle);
CkRest_AddHeader(rest,'Accept','text/event-stream');
CkRest_AddHeader(rest,'Cache-Control','no-cache');
responseBody := CkRest__fullRequestNoBody(rest,'GET','/.json');
// A 307 redirect response is expected.
if (CkRest_getResponseStatusCode(rest) <> 307) then
begin
Memo1.Lines.Add('Unexpected response code: ' + IntToStr(CkRest_getResponseStatusCode(rest)));
Memo1.Lines.Add(responseBody);
Memo1.Lines.Add('Failed.');
Exit;
end;
// Get the redirect URL
urlStr := CkRest__lastRedirectUrl(rest);
url := CkUrl_Create();
CkUrl_ParseUrl(url,urlStr);
Memo1.Lines.Add('redirect URL domain: ' + CkUrl__host(url));
Memo1.Lines.Add('redirect URL path: ' + CkUrl__path(url));
Memo1.Lines.Add('redirect URL query params: ' + CkUrl__query(url));
Memo1.Lines.Add('redirect URL path with query params: ' + CkUrl__pathWithQueryParams(url));
// Our text/event-stream will be obtained from the redirect URL...
rest2 := CkRest_Create();
success := CkRest_Connect(rest2,CkUrl__host(url),443,True,True);
if (success <> True) then
begin
Memo1.Lines.Add(CkRest__lastErrorText(rest2));
Exit;
end;
CkRest_AddHeader(rest2,'Accept','text/event-stream');
CkRest_AddHeader(rest2,'Cache-Control','no-cache');
// Add the redirect query params to the request
CkRest_AddQueryParams(rest2,CkUrl__query(url));
// In our case, we don't actually need the auth query param,
// so remove it.
CkRest_RemoveQueryParam(rest2,'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.)
success := CkRest_SendReqNoBody(rest2,'GET',CkUrl__path(url));
if (success <> True) then
begin
Memo1.Lines.Add(CkRest__lastErrorText(rest2));
Exit;
end;
// 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.
responseStatusCode := CkRest_ReadResponseHeader(rest2);
if (responseStatusCode < 0) then
begin
Memo1.Lines.Add(CkRest__lastErrorText(rest2));
Exit;
end;
// If successful, a 200 response code is expected.
// If the reponse code is not 200, then read the response body and fail..
if (responseStatusCode <> 200) then
begin
Memo1.Lines.Add('Response Code: ' + IntToStr(responseStatusCode));
Memo1.Lines.Add('Response Status Text: ' + CkRest__responseStatusText(rest2));
Memo1.Lines.Add('Response Header: ' + CkRest__responseHeader(rest2));
responseBody := CkRest__readRespBodyString(rest2);
if (CkRest_getLastMethodSuccess(rest2) = True) then
begin
Memo1.Lines.Add('Error Response Body: ' + responseBody);
end;
Memo1.Lines.Add('Failed.');
Exit;
end;
// For this example, our JSON database will be empty at the beginning.
// The incoming events (put and patch) will be applied to this database.
jsonDb := CkJsonObject_Create();
// Make sure to set the JSON path delimiter to "/". The default is "." and this
// is not compatible with Firebase paths.
CkJsonObject_putDelimiterChar(jsonDb,'/');
// 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..
eventStream := CkStream_Create();
// This sse object will be used as a helper to parse the server-sent event stream.
sse := CkServerSentEvent_Create();
task := CkRest_ReadRespBodyStreamAsync(rest2,eventStream,True);
CkTask_Run(task);
// For this example, we'll just read a few events, and then cancel the
// async task.
count := 0;
while (count < 3) and (CkTask_getFinished(task) = False) do
begin
// 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.
eventStr := CkStream__readUntilMatch(eventStream,#13#10 + #13#10);
if (CkStream_getLastMethodSuccess(eventStream) <> True) then
begin
Memo1.Lines.Add(CkStream__lastErrorText(eventStream));
// Force the loop to exit by setting the count to a high number.
count := 99999;
end
else
begin
Memo1.Lines.Add('Event: [' + eventStr + ']');
// We have an event. Let's update our local copy of the JSON database.
success := CkServerSentEvent_LoadEvent(sse,eventStr);
if (success <> True) then
begin
Memo1.Lines.Add('Failed to load sse event: ' + eventStr);
end
else
begin
// Now we can easily access the event name and data, and apply it to our JSON database:
success := CkJsonObject_FirebaseApplyEvent(jsonDb,CkServerSentEvent__eventName(sse),CkServerSentEvent__data(sse));
if (success <> True) then
begin
Memo1.Lines.Add('Failed to apply event: ' + CkServerSentEvent__eventName(sse) + ': ' + CkServerSentEvent__data(sse));
end
else
begin
Memo1.Lines.Add('Successfully applied event: ' + CkServerSentEvent__eventName(sse) + ': ' + CkServerSentEvent__data(sse));
end;
end;
end;
count := count + 1;
end;
// Make sure the background task is cancelled if still running.
CkTask_Cancel(task);
CkTask_Dispose(task);
// Examine the JSON database after applying events..
CkJsonObject_putEmitCompact(jsonDb,False);
Memo1.Lines.Add('----');
Memo1.Lines.Add(CkJsonObject__emit(jsonDb));
CkFileAccess_Dispose(fac);
CkRest_Dispose(rest);
CkAuthGoogle_Dispose(authGoogle);
CkUrl_Dispose(url);
CkRest_Dispose(rest2);
CkJsonObject_Dispose(jsonDb);
CkStream_Dispose(eventStream);
CkServerSentEvent_Dispose(sse);