realtimetraffic/src/realtimetraffic/conn.go

/*
* Copyright (C) 2014 struktur AG
* http://www.strukturag.com
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
*   http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* This file is baeed on ideas from the chat example of gorilla/websocket.
* Copyright 2013 Gary Burd. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without modification,
* are permitted provided that the following conditions are met:
*
*  Redistributions of source code must retain the above copyright notice, this
*  list of conditions and the following disclaimer.
*
*  Redistributions in binary form must reproduce the above copyright notice, this
*  list of conditions and the following disclaimer in the documentation and/or
*  other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
* ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
* ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package main

import (
	"github.com/gorilla/websocket"
	"log"
	"net/http"
	"time"
)

const (
	writeWait      = 10 * time.Second
	pongWait       = 60 * time.Second
	pingPeriod     = (pongWait * 9) / 10
	maxMessageSize = 512
)

type connection struct {
	ws    *websocket.Conn
	send  chan []byte
	iface string
}

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 {
		_, _, err := c.ws.ReadMessage()
		if err != nil {
			break
		}
	}
}

func (c *connection) write(mt int, payload []byte) error {
	c.ws.SetWriteDeadline(time.Now().Add(writeWait))
	return c.ws.WriteMessage(mt, payload)
}

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
			}
		}
	}
}

func serveWs(w http.ResponseWriter, r *http.Request) {
	if r.Method != "GET" {
		http.Error(w, "Method not allowed", 405)
		return
	}

	// Read request details.
	r.ParseForm()
	iface := r.FormValue("if")
	if iface == "" {
		iface = "eth0"
	}

	ws, err := websocket.Upgrade(w, r, nil, 1024, 1024)
	if _, ok := err.(websocket.HandshakeError); ok {
		http.Error(w, "Not a websocket handshake", 400)
		return
	} else if err != nil {
		log.Println(err)
		return
	}
	c := &connection{send: make(chan []byte, 256), ws: ws, iface: iface}
	h.register <- c
	go c.writePump()
	c.readPump()
}