Server-Sent Events for iOS, watchOS, tvOS and macOS
For details on Server Sent Events, see the Specification
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:, onMessage, 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.
To make the initial connection to the streaming event server, call open on the event source. That gives you control over when events start arriving.
NSURL *serverURL = [NSURL URLWithString:@"http://127.0.0.1:8000/"];
EventSource *source = [EventSource eventSourceWithURL:serverURL];
[source onMessage:^(Event *e) {
NSLog(@"%@: %@", e.event, e.data);
}];
[source open];Reconnection attempts are automatic and seamless, even if the server goes down. How frequently reconnection attempts are made is controlled by the server by setting the retry key on its events. If the server doesn't send a retry, the default is 1 second intervals.
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.
EventSource supports multiple methods for installing the library in a project.
CocoaPods is a dependency manager for Objective-C, which automates and simplifies the process of using 3rd-party libraries like EventSource in your projects. You can install it with the following command:
$ gem install cocoapodsTo integrate EventSource into your Xcode project using CocoaPods, specify it in your Podfile:
source 'https://github.com/CocoaPods/Specs.git'
platform :ios, '8.0'
target 'TargetName' do
pod 'DarklyEventSource', '~> 4.0.2'
endThen, run the following command:
$ pod installCarthage is a decentralized dependency manager that builds your dependencies and provides you with binary frameworks.
You can install Carthage with Homebrew using the following command:
$ brew update
$ brew install carthageTo integrate EventSource into your Xcode project using Carthage, specify it in your Cartfile:
github "launchdarkly/ios-eventsource" >= 4.0.2
Run carthage to build the framework and drag the built EventSource.framework into your Xcode project.
Copyright (c) 2013 Neil Cowburn (http://github.com/neilco/)
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