(C#) Firebase Receive Server-Sent Events (text/event-stream)

Demonstrates how to start receiving server-sent events and update your JSON database with each event.

Chilkat .NET Downloads Chilkat .NET Framework Chilkat for .NET Core

// 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.
Chilkat.FileAccess fac = new Chilkat.FileAccess();
string accessToken = fac.ReadEntireTextFile("qa_data/tokens/firebaseToken.txt","utf-8");
if (fac.LastMethodSuccess != true) {
    Debug.WriteLine(fac.LastErrorText);
    return;
}

Chilkat.Rest rest = new Chilkat.Rest();

// 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.  
bool success = rest.Connect("chilkat.firebaseio.com",443,true,true);
if (success != true) {
    Debug.WriteLine(rest.LastErrorText);
    return;
}

Chilkat.AuthGoogle authGoogle = new Chilkat.AuthGoogle();
authGoogle.AccessToken = accessToken;
rest.SetAuthGoogle(authGoogle);

rest.AddHeader("Accept","text/event-stream");
rest.AddHeader("Cache-Control","no-cache");

string responseBody = rest.FullRequestNoBody("GET","/.json");

// A 307 redirect response is expected.
if (rest.ResponseStatusCode != 307) {
    Debug.WriteLine("Unexpected response code: " + Convert.ToString(rest.ResponseStatusCode));
    Debug.WriteLine(responseBody);
    Debug.WriteLine("Failed.");
    return;
}

// Get the redirect URL
Chilkat.Url url = rest.RedirectUrl();
if (rest.LastMethodSuccess != true) {
    Debug.WriteLine(rest.LastErrorText);
    return;
}

Debug.WriteLine("redirect URL domain: " + url.Host);
Debug.WriteLine("redirect URL path: " + url.Path);
Debug.WriteLine("redirect URL query params: " + url.Query);
Debug.WriteLine("redirect URL path with query params: " + url.PathWithQueryParams);

// Our text/event-stream will be obtained from the redirect URL...
Chilkat.Rest rest2 = new Chilkat.Rest();

success = rest2.Connect(url.Host,443,true,true);
if (success != true) {
    Debug.WriteLine(rest2.LastErrorText);

    return;
}

rest2.AddHeader("Accept","text/event-stream");
rest2.AddHeader("Cache-Control","no-cache");

// Add the redirect query params to the request
rest2.AddQueryParams(url.Query);

// In our case, we don't actually need the auth query param,
// so remove it.
rest2.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.)
success = rest2.SendReqNoBody("GET",url.Path);
if (success != true) {
    Debug.WriteLine(rest2.LastErrorText);

    return;
}

// 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.
int responseStatusCode = rest2.ReadResponseHeader();
if (responseStatusCode < 0) {
    Debug.WriteLine(rest2.LastErrorText);
    return;
}

// 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) {
    Debug.WriteLine("Response Code: " + Convert.ToString(responseStatusCode));
    Debug.WriteLine("Response Status Text: " + rest2.ResponseStatusText);
    Debug.WriteLine("Response Header: " + rest2.ResponseHeader);
    responseBody = rest2.ReadRespBodyString();
    if (rest2.LastMethodSuccess == true) {
        Debug.WriteLine("Error Response Body: " + responseBody);
    }

    Debug.WriteLine("Failed.");
    return;
}

// For this example, our JSON database will be empty at the beginning.
// The incoming events (put and patch) will be applied to this database.
Chilkat.JsonObject jsonDb = new Chilkat.JsonObject();

// Make sure to set the JSON path delimiter to "/".  The default is "." and this
// is not compatible with Firebase paths.
jsonDb.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..
Chilkat.Stream eventStream = new Chilkat.Stream();

// This sse object will be used as a helper to parse the server-sent event stream.
Chilkat.ServerSentEvent sse = new Chilkat.ServerSentEvent();

Chilkat.Task task = rest2.ReadRespBodyStreamAsync(eventStream,true);
task.Run();

// For this example, we'll just read a few events, and then cancel the
// async task.
int count = 0;
while ((count < 3) && (task.Finished == false)) {

    // 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.
    string eventStr = eventStream.ReadUntilMatch("\r\n\r\n");
    if (eventStream.LastMethodSuccess != true) {
        Debug.WriteLine(eventStream.LastErrorText);
        // Force the loop to exit by setting the count to a high number.
        count = 99999;
    }
    else {
        Debug.WriteLine("Event: [" + eventStr + "]");

        // We have an event. Let's update our local copy of the JSON database.
        success = sse.LoadEvent(eventStr);
        if (success != true) {
            Debug.WriteLine("Failed to load sse event: " + eventStr);
        }
        else {
            // Now we can easily access the event name and data, and apply it to our JSON database:
            success = jsonDb.FirebaseApplyEvent(sse.EventName,sse.Data);
            if (success != true) {
                Debug.WriteLine("Failed to apply event: " + sse.EventName + ": " + sse.Data);
            }
            else {
                Debug.WriteLine("Successfully applied event: " + sse.EventName + ": " + sse.Data);
            }

        }

    }

    count = count + 1;
}

// Make sure the background task is cancelled if still running.
task.Cancel();

// Examine the JSON database after applying events..
jsonDb.EmitCompact = false;
Debug.WriteLine("----");
Debug.WriteLine(jsonDb.Emit());