{"id":378,"date":"2019-03-03T23:54:53","date_gmt":"2019-03-03T18:24:53","guid":{"rendered":"http:\/\/uitutorials.in\/wp\/?p=378"},"modified":"2019-09-30T10:34:09","modified_gmt":"2019-09-30T05:04:09","slug":"server-sent-events","status":"publish","type":"post","link":"https:\/\/uitutorials.in\/wp\/server-sent-events\/","title":{"rendered":"Server-sent events"},"content":{"rendered":"

Server-Sent Events utilize a regular HTTP octet streams,<\/strong> and therefore are limited to the browser\u2019s connection pool limit of ~6 concurrent HTTP connections per server<\/a>. But they provide a standard way of pushing data from the server to the clients over HTTP,<\/strong> which load balancers and proxies understand out-of-the-box. The biggest advantage being that, exactly as WebSockets, they utilize only one TCP connection.<\/strong> The biggest disadvantage is that Server-Sent Events don\u2019t provide a mechanism to detect dropped clients<\/strong> until a message is sent.<\/p>\n

\"\"<\/p>\n

They are standardized via HTML 5<\/a>, most HTTP servers support them out-of-the-box, and they are available in most browsers except for Internet Explorer and Edge<\/a> where they are available through a polyfill<\/a>.<\/p>\n

Rails, Roda and Sinatra support them out-of-the-box. And they have a simple protocol\u200a\u2014\u200apayloads are just prefixed with one of the following keywords data:, event:, id: and retry:. data: is used to push a payload, event: is optional and indicates the type of data being pushed, id: is also optional and indicates the event\u2019s ID, finally retry: instructs the client to change it\u2019s connection retry timeout\u200a\u2014\u200aunlike WebSockets, Server-Sent Events have a reconnect mechanism built-in,<\/strong> though this is a feature that most WebSocket libraries add any way.<\/p>\n

to send data to other clients a regular HTTP POST request is made to <\/strong>the server. A heartbeat is kept to keep the connections alive (WebSockets also do that) and to detect dropped clients (since dropped connections can only be detected when data is pushed to them).<\/p>\n

Reference<\/h3>\n