3.3 KiB
3.3 KiB
Overview
"SSEs are sent over traditional HTTP. That means they do not require a special protocol or server implementation to get working. WebSockets on the other hand, require full-duplex connections and new Web Socket servers to handle the protocol. In addition, Server-Sent Events have a variety of features that WebSockets lack by design such as automatic reconnection, event IDs, and the ability to send arbitrary events." -- html5rocks
Example
#include <map>
#include <chrono>
#include <string>
#include <memory>
#include <cstdlib>
#include <restbed>
using namespace std;
using namespace restbed;
using namespace std::chrono;
vector< shared_ptr< Session > > sessions;
void register_event_source_handler( const shared_ptr< Session > session )
{
const auto headers = multimap< string, string > {
{ "Connection", "keep-alive" },
{ "Cache-Control", "no-cache" },
{ "Content-Type", "text/event-stream" },
{ "Access-Control-Allow-Origin", "*" } //Only required for demo purposes.
};
session->yield( OK, headers, [ ]( const shared_ptr< Session > session )
{
sessions.push_back( session );
} );
}
void event_stream_handler( void )
{
static size_t counter = 0;
const auto message = "data: event " + to_string( counter ) + "\n\n";
sessions.erase(
std::remove_if(sessions.begin(), sessions.end(),
[](const shared_ptr<Session> &a) {
return a->is_closed();
}),
sessions.end());
for ( auto session : sessions )
{
session->yield( message );
}
counter++;
}
int main( const int, const char** )
{
auto resource = make_shared< Resource >( );
resource->set_path( "/stream" );
resource->set_method_handler( "GET", register_event_source_handler );
auto settings = make_shared< Settings >( );
settings->set_port( 1984 );
auto service = make_shared< Service >( );
service->publish( resource );
service->schedule( event_stream_handler, seconds( 2 ) );
service->start( settings );
return EXIT_SUCCESS;
}
Build
$ clang++ -o example example.cpp -l restbed
Execution
$ ./example
Client
<!DOCTYPE HTML>
<html>
<head>
<script type="text/javascript">
function add_event( data )
{
var li = document.createElement( "li" );
li.appendChild( document.createTextNode( "> " + data ) );
var ul = document.getElementById( "events" );
ul.appendChild( li );
}
if ( !!window.EventSource )
{
var source = new EventSource( "http://localhost:1984/stream" );
source.addEventListener( "message", function( evt )
{
add_event( evt.data );
}, false );
source.addEventListener( "open", function( evt )
{
add_event( "EventSource open." );
}, false );
source.addEventListener( 'error', function( evt )
{
if ( evt.readyState == EventSource.CLOSED )
{
add_event( "EventSource closed." );
}
}, false );
}
else
{
alert( "WebSockets NOT supported by your Browser!" );
}
</script>
</head>
<body>
<h1>Incoming Events</h1>
<ul id="events">
</ul>
</body>
</html>