What are Server-Sent Events (SSE)?

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“Everyone i m trisha carr neelakantham. Welcome back to a bleep quickvids in this video. Video. We learn all about service and events or ssc.

How they re different from websocket protocol. That abele primarily operates on see the different use cases and finally look at how you can use ss ii. As a super lightweight. Way to subscribe to messages.

Published using a breeze. Without even needing to install a client sdk. If you look at the data sharing spectrum on the internet. It originally started with http for static.

1 of requests and responses with the advent of event driven frequent updates it soon began moving towards http polling. Where you frequently send new requests and get responses back further on too long polling. Where the server minimizes empty responses by holding on to the connection and avoiding sending a response unless..


It has some data to return as this was very inefficient for event driven real time applications wanting no more than just a few hundred milliseconds worth of delay. The data sharing spectrums or new protocol websockets. Which is essentially a bi directional duplex. Connection starting off as a regular http request.

But with a special upgrade header this allows simultaneous communication between a server and a client in both directions leading to what we now know as push mechanism of sharing data. Where the server can simply send new updates as they happen without waiting for the client to request each time now. This is where it gets interesting while websocket solves. The real time use case scenario for the majority of the applications and devices out there it may get a little heavy in some cases for battery constrained devices.

Such as the ones in iot. One would gently prefer using mqtt at a blee while we do support mq dt wire protocol adapter. We ve come to realize that with data sharing moving more and more towards streaming. Even mqtt might be an overkill in some scenarios.

And as such this other standard called service and events or sse could be really useful in some niche use cases sse is a lightweight protocol on top of http streaming that allows super lightweight subscribe only capabilities to clients unlike websockets sec does not provide a communication pathway. But can be used by the server s to push data to the clients in real time. This is especially useful in cases where a client is just interested in subscribing to a stream of data without needing to communicate back with the server in the same connection like in a data stream containing cryptocurrency prizes sse was standardized as part of html5 by the w3c and offers a very simple api called the even source..


All the major browsers have inbuilt support for this api allowing you to make use of ssese capabilities directly without needing to install any kind of a library or plugin whatsoever. Let s now have a quick look at how you can use sse to subscribe to messages and events on a blazed channels for those of you who are new to a blee just a quick reminder that channels are the basic unit of data transfer enabling publishers publish data into one or more channels for subscribers of those channels to receive updates in real time as part of sec abele offers two endpoints that your clients can connect to in order to be able to receive a continuous stream of updates from a data publisher via channels. One of them is the basic even stream. Which sends new event updates in json format.

The other one is sse which starts a streaming http request that confirms to the standardized sse spec. For ease of consumption using an sse library in this demo. We ll look at an example with the sse endpoint for this video. I ll be utilizing one of the open data streams publicly hosted on the abele hub provisioned by a believes new api streamer that allows management of data streams for publishers.

And subscribers. Let s go ahead and pick the bitcoin pricing product as it updates. Fairly frequently. I ll be using glitch for this demo.

It s a simple open source tool to host sample code as you can see here. We have the basic web. Page setup with a html file and a javascript file..


The html file. Contains. The basic layout. We have a list element.

Which will populate dynamically with new price updates as we receive them some basic styling and finally a link to our javascript file. This is how it would look visually in our javascript file. I ve already included an abler api key as well as a channel name that i got from the bitcoin product documentation on the ibly hub. Now let s go ahead and specify the url with the sse endpoint our api key and the channel name not that you can specify multiple channels in a comma separated format next.

Let s define a new even source instance and pass in our url to it let s add a reference to the list element that we specified on our html file with the id of events before we move forward let s also define a function called add event. Which basically would log various events to the list element inside our textbox next. Let s specify the various handlers that come with the event source api starting with the on open when the streaming connection opens. We ll simply log.

It as a message in our text box next is the on message handler. Which is triggered when an update is received even in this case. We ll simply log the event..


Name and data in our text box. Finally. The own error handler to handle errors will add a check to see if there s an error message. If yes just log that message otherwise.

We simply log an error connecting to a blee message that s it simple as that note that we didn t include or use any sdk or library. Including a blee. Let s see if this works and it does as you can see with sse with only a few lines of code. We can add subscribe only capabilities to our clients.

While it s lightweight and easy to implement. We still recommend that you use a belize client sdks wherever possible that s all for this eglee. Quick bit. I ll see you all in the next.

Quick bit video with some other interesting info as usual you can find links to all the related resources like dogs tutorials and the demo labs in the description of this video. ” ..

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