pubsub.go

// Go PubSub Server
//
// Usage - Subscribing:
// 	var conn = new EventSource('/subscribe');
// 	conn.addEventListener('message', function(e){ alert(e.data); }, false);
//
// Usage - Publishing:
// 	curl http://localhost:8080/publish -F 'msg=Hello World'

package main

import (
	"net/http"
)

var channels []chan string

func publish(w http.ResponseWriter, r *http.Request) {
	msg := r.FormValue("msg")
	for _, channel := range channels {
		channel <- msg
	}
	w.WriteHeader(204)
}

func subscribe(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "text/event-stream")
	w.Header().Set("Connection", "keep-alive")
	w.WriteHeader(200)

	channel  := make(chan string)
	channels = append(channels, channel)

	f, f_ok := w.(http.Flusher)

	for {
		msg := <-channel
		w.Write([]byte("data: " + msg + "\n\n"))
		if f_ok {
			f.Flush()
		}
	}
}

func main() {
	http.HandleFunc("/publish", publish)
	http.HandleFunc("/subscribe", subscribe)
	http.ListenAndServe(":8080", nil)
}