137 lines
3.3 KiB
Markdown
137 lines
3.3 KiB
Markdown
|
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](https://www.html5rocks.com/en/tutorials/eventsource/basics/)
|
||
|
|
|
||
|
|
Example
|
||
|
|
-------
|
||
|
|
|
||
|
|
```C++
|
||
|
|
#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
|
||
|
|
------
|
||
|
|
```HTML
|
||
|
|
<!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>
|
||
|
|
```
|