Server-Sent Events for iOS and Mac
It creates a long-lived, unidirectional HTTP channel between your Cocoa app and a web server so that your app can receive events from the server.
Subscribing to a named event is done via the addEventListener:handler: method, as shown below:
NSURL *serverURL = [NSURL URLWithString:@"http://127.0.0.1:8000/"];
EventSource *source = [EventSource eventSourceWithURL:serverURL];
[source addEventListener:@"hello_event" handler:^(Event *e) {
NSLog(@"%@: %@", e.event, e.data);
}];It's super simple and will be familiar to anyone who has seen any Server-Sent Events JavaScript code.
There's a onMessage: method that will receive all message events from the server.
NSURL *serverURL = [NSURL URLWithString:@"http://127.0.0.1:8000/"];
EventSource *source = [EventSource eventSourceWithURL:serverURL];
[source onMessage:^(Event *e) {
NSLog(@"%@: %@", e.event, e.data);
}];Additionally, there are onOpen:, onError:, and onReadyStateChanged: methods to receive connection state events.
NSURL *serverURL = [NSURL URLWithString:@"http://127.0.0.1:8000/"];
EventSource *source = [EventSource eventSourceWithURL:serverURL];
[source onError:^(Event *e) {
NSLog(@"ERROR: %@", e.data);
}];With the exception of the onError:, the event and data properties for these events will be null. Check the readyState property on the event.
Reconnection attempts are automatic and seamless, even if the server goes go. How frequently reconnection attempts are made is controlled by the server by setting the retry key on its events.
This is a simple Node.js app that will generate the Server-Sent Events. The events are created at a rate of one per second.
var http = require('http');
http.createServer(function (req, res) {
res.writeHead(200, { 'Transfer-Encoding': 'chunked', 'Content-Type': 'text/event-stream' });
setInterval(function() {
var now = new Date().getTime();
var payload = 'event: hello_event\ndata: {"message":"' + now + '"}\n\n';
res.write(payload);
}, 1000);
}).listen(8000);
The payload above doesn't include an id parameter, but if you include one it will be available in the Event object in your Cocoa code.
There is also a simple Go Server-Sent Events server.
The easiest way to get started is to use Carthage. Just add the following line to your Cartfile and the run carthage update from your terminal:
github "neilco/EventSource"If you prefer Cocoapods, add this to your Podfile and then run pod install from your terminal:
pod 'EventSource'Otherwise, just include the contents of the EventSource directory manually to your project.
I'm @neilco on GitHub and I'm @neilco on Twitter.
Copyright (c) 2013 Neil Cowburn (http://github.com/neilco/)
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