server.go

package main

import (
	"fmt"
	"log"
	"net/http"
	"strconv"
	"time"

	"github.com/gorilla/websocket"
)

const (
	// Time allowed to write a message to the peer.
	writeWait = 10 * time.Second

	// Time allowed to read the next pong message from the peer.
	pongWait = 60 * time.Second

	// Send pings to peer with this period. Must be less than pongWait.
	pingPeriod = (pongWait * 9) / 10

	// Maximum message size allowed from peer.
	maxMessageSize = 512
)

func main() {
	go h.run()
	serverMap := make(map[int]*http.ServeMux)

	for i := 8001; i <= 8050; i++ {
		port := i
		serverMap[port] = http.NewServeMux()
		serverMap[port].HandleFunc("/ws", serveWs)
		go func(server *http.ServeMux, port int) {
			fmt.Println("Listening for websocket connections on port " + strconv.Itoa(port))
			err := http.ListenAndServe(":"+strconv.Itoa(port), server)
			if err != nil {
				log.Fatal("ListenAndServe: ", err)
			}
		}(serverMap[port], port)
	}

	quit := make(chan bool)
	<-quit

}

// hub maintains the set of active connections and broadcasts messages to the
// connections.
type hub struct {
	// Registered connections.
	connections map[*connection]bool

	// Inbound messages from the connections.
	broadcast chan []byte

	// Register requests from the connections.
	register chan *connection

	// Unregister requests from connections.
	unregister chan *connection
}

var h = hub{
	broadcast:   make(chan []byte),
	register:    make(chan *connection),
	unregister:  make(chan *connection),
	connections: make(map[*connection]bool),
}

func (h *hub) run() {
	for {
		select {
		case c := <-h.register:
			h.connections[c] = true
			fmt.Println("Number of connections: " + strconv.Itoa(len(h.connections)))
		case c := <-h.unregister:
			if _, ok := h.connections[c]; ok {
				delete(h.connections, c)
				close(c.send)
			}
		case m := <-h.broadcast:
			for c := range h.connections {
				select {
				case c.send <- m:
				default:
					close(c.send)
					delete(h.connections, c)
				}
			}
		}
	}
}

var upgrader = websocket.Upgrader{
	ReadBufferSize:  1024,
	WriteBufferSize: 1024,
	CheckOrigin:     originCheck,
}

// connection is an middleman between the websocket connection and the hub.
type connection struct {
	// The websocket connection.
	ws *websocket.Conn

	// Buffered channel of outbound messages.
	send chan []byte
}

// readPump pumps messages from the websocket connection to the hub.
func (c *connection) readPump() {
	defer func() {
		h.unregister <- c
		c.ws.Close()
	}()
	c.ws.SetReadLimit(maxMessageSize)
	c.ws.SetReadDeadline(time.Now().Add(pongWait))
	c.ws.SetPongHandler(func(string) error { c.ws.SetReadDeadline(time.Now().Add(pongWait)); return nil })
	for {
		_, message, err := c.ws.ReadMessage()
		if err != nil {
			break
		}
		h.broadcast <- message
	}
}

// write writes a message with the given message type and payload.
func (c *connection) write(mt int, payload []byte) error {
	c.ws.SetWriteDeadline(time.Now().Add(writeWait))
	return c.ws.WriteMessage(mt, payload)
}

// writePump pumps messages from the hub to the websocket connection.
func (c *connection) writePump() {
	ticker := time.NewTicker(pingPeriod)
	defer func() {
		ticker.Stop()
		c.ws.Close()
	}()
	for {
		select {
		case message, ok := <-c.send:
			if !ok {
				c.write(websocket.CloseMessage, []byte{})
				return
			}
			if err := c.write(websocket.TextMessage, message); err != nil {
				return
			}
		case <-ticker.C:
			if err := c.write(websocket.PingMessage, []byte{}); err != nil {
				return
			}
		}
	}
}

// serverWs handles websocket requests from the peer.
func serveWs(w http.ResponseWriter, r *http.Request) {

	if r.Method != "GET" {
		http.Error(w, "Method not allowed", 405)
		return
	}
	ws, err := upgrader.Upgrade(w, r, nil)
	if err != nil {
		log.Println(err)
		return
	}
	c := &connection{send: make(chan []byte, 256), ws: ws}
	h.register <- c
	go c.writePump()
	c.readPump()
}

func originCheck(req *http.Request) bool {
	return true
}