137 lines
3.3 KiB
Markdown
137 lines
3.3 KiB
Markdown
Overview
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--------
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"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/)
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Example
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-------
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```C++
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#include <map>
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#include <chrono>
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#include <string>
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#include <memory>
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#include <cstdlib>
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#include <restbed>
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using namespace std;
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using namespace restbed;
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using namespace std::chrono;
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vector< shared_ptr< Session > > sessions;
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void register_event_source_handler( const shared_ptr< Session > session )
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{
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const auto headers = multimap< string, string > {
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{ "Connection", "keep-alive" },
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{ "Cache-Control", "no-cache" },
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{ "Content-Type", "text/event-stream" },
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{ "Access-Control-Allow-Origin", "*" } //Only required for demo purposes.
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};
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session->yield( OK, headers, [ ]( const shared_ptr< Session > session )
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{
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sessions.push_back( session );
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} );
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}
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void event_stream_handler( void )
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{
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static size_t counter = 0;
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const auto message = "data: event " + to_string( counter ) + "\n\n";
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sessions.erase(
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std::remove_if(sessions.begin(), sessions.end(),
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[](const shared_ptr<Session> &a) {
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return a->is_closed();
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}),
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sessions.end());
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for ( auto session : sessions )
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{
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session->yield( message );
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}
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counter++;
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}
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int main( const int, const char** )
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{
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auto resource = make_shared< Resource >( );
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resource->set_path( "/stream" );
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resource->set_method_handler( "GET", register_event_source_handler );
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auto settings = make_shared< Settings >( );
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settings->set_port( 1984 );
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auto service = make_shared< Service >( );
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service->publish( resource );
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service->schedule( event_stream_handler, seconds( 2 ) );
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service->start( settings );
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return EXIT_SUCCESS;
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}
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```
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Build
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-----
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> $ clang++ -o example example.cpp -l restbed
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Execution
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---------
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> $ ./example
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Client
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------
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```HTML
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<!DOCTYPE HTML>
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<html>
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<head>
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<script type="text/javascript">
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function add_event( data )
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{
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var li = document.createElement( "li" );
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li.appendChild( document.createTextNode( "> " + data ) );
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var ul = document.getElementById( "events" );
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ul.appendChild( li );
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}
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if ( !!window.EventSource )
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{
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var source = new EventSource( "http://localhost:1984/stream" );
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source.addEventListener( "message", function( evt )
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{
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add_event( evt.data );
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}, false );
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source.addEventListener( "open", function( evt )
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{
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add_event( "EventSource open." );
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}, false );
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source.addEventListener( 'error', function( evt )
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{
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if ( evt.readyState == EventSource.CLOSED )
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{
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add_event( "EventSource closed." );
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}
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}, false );
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}
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else
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{
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alert( "WebSockets NOT supported by your Browser!" );
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}
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</script>
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</head>
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<body>
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<h1>Incoming Events</h1>
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<ul id="events">
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</ul>
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</body>
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</html>
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```
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