c. 发送消息
当socket处于打开状态（即调用onopen监听程序之后，调用onclose监听程序之前），可以使用send方法发送消息。
ws.send("Hello World");
三、HTML5 WebSockets 应用示例
本节将结合前面讲述的Geolocation接口来创建一个直接在Web页面中计算距离的应用。
1、编写HTML文件
<!DOCTYPE html></p>
<p><html></p>
<p> <head></p>
<p> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"></p>
<p> <title>HTML5 WebSocket / Geolocation 追踪器</title></p>
<p> <link rel="stylesheet" href="styles.css"></p>
<p> </head></p>
<p> <body onload="loadDemo()"></p>
<p> <h1>HTML5 WebSocket / Geolocation 追踪器</h1></p>
<p> <div><strong>Geolocation</strong>: <p id="geoStatus">你的浏览器不支持HTML5 Geolocation</p></div></p>
<p> <div><strong>WebSocket</strong>: <p id="socketStatus">你的浏览器不支持HTML5 Web Sockets</p></div></p>
<p> </body></p>
<p></html>
2、添加WebSocket代码
function loadDemo(){
//确保浏览器支持WebSocket
if(window.WebSocket){
url = "ws://localhost:8080";//broadcast WebSocket服务器位置
ws = new WebSocket(url);
ws.onopen = function(){
updateSocketStatus("连接已建立");
}
ws.onmessage = function(e){
updateSocketeStatus("更新位置数据：" + dataReturned(e.data));
}
}
}
3、添加Geolocation代码
var geo;
if(navigator.geolocation){
geo = navigator.geolocation;
updateGeolocationStatus("浏览器支持HTML5 Geolocation");
}</p>
<p>geo.watchPosition(updateLocation,handleLocationError,{maximumAge:20000});//每20s更新一次</p>
<p>function updateLocation(position){
var latitude = position.coords.latitude;
var longitude = position.coords.longitude;
var timestamp = position.timestamp;
updateGeolocationStatus("位置更新时间：" + timestamp);
var toSend = JSON.stringify([myId,latitude,longitude]);
sendMyLocation(toSend);
}
4、合并所有内容
<!DOCTYPE html></p>
<p><html></p>
<p> <head></p>
<p> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"></p>
<p> <title>HTML5 WebSocket / Geolocation 追踪器</title></p>
<p> <link rel="stylesheet" href="styles.css"></p>
<p> </head></p>
<p> <body onload="loadDemo()"></p>
<p> <h1>HTML5 WebSocket / Geolocation 追踪器</h1></p>
<p> <div><strong>Geolocation</strong>: <p id="geoStatus">你的浏览器不支持HTML5 Geolocation</p></div></p>
<p> <div><strong>WebSocket</strong>: <p id="socketStatus">你的浏览器不支持HTML5 Web Sockets</p></div></p>
<p> </body></p>
<p> <script></p>
<p> //WebSocket的引用</p>
<p> var ws;</p>
<p> //为该会话生成的唯一随机的ID</p>
<p> var myId = Math.floor(100000*Math.random());</p>
<p> //当前显示的行数</p>
<p> var rowCount;</p>
<p> function updateSocketStatus(message){</p>
<p> document.getElementById("socketStatus").innerHTML = message;</p>
<p> }</p>
<p> function updateGeolocationStatus(message){</p>
<p> document.getElementById("geoStatus").innerHTML = message;</p>
<p> }</p>
<p> function loadDemo(){</p>
<p> //确保浏览器支持WebSocket</p>
<p> if(window.WebSocket){</p>
<p> url = "ws://localhost:8080";//broadcast WebSocket服务器位置</p>
<p> ws = new WebSocket(url);</p>
<p> ws.onopen = function(){</p>
<p> updateSocketStatus("连接已建立");</p>
<p> }</p>
<p> ws.onmessage = function(e){</p>
<p> updateSocketStatus("更新位置数据：" + dataReturned(e.data));</p>
<p> }</p>
<p> }</p>
<p> var geo;</p>
<p> if(navigator.geolocation){</p>
<p> geo = navigator.geolocation;</p>
<p> updateGeolocationStatus("浏览器支持HTML5 Geolocation");</p>
<p> }</p>
<p> geo.watchPosition(updateLocation,handleLocationError,{maximumAge:20000});//每20s更新一次</p>
<p> function updateLocation(position){</p>
<p> var latitude = position.coords.latitude;</p>
<p> var longitude = position.coords.longitude;</p>
<p> var timestamp = position.timestamp;</p>
<p> updateGeolocationStatus("位置更新时间：" + timestamp);</p>
<p> var toSend = JSON.stringify([myId,latitude,longitude]);</p>
<p> sendMyLocation(toSend);</p>
<p> }</p>
<p> function sendMyLocation(newLocation){</p>
<p> if(ws){</p>
<p> ws.send(newLocation)</p>
<p> }</p>
<p> }</p>
<p> function dataReturned(locationData){</p>
<p> var allData = JSON.parse(locationData);</p>
<p> var incomingId = allData[1];</p>
<p> var incomingLat = allData[2];</p>
<p> var incomingLong = allData[3];</p>
<p> var incomingRow = document.getElementById(incomingId);</p>
<p> if(!incomingRow){</p>
<p> incomingRow = document.getElementById("div");</p>
<p> incomingRow.setAttribute("id",incomingId);</p>
<p> incomingRow.userText = (incomingId == myId)?"Me":'User' + rowCount;</p>
<p> rowCount++;</p>
<p> document.body.appendChild(incomingRow);</p>
<p> }</p>
<p> incomingRow.innerHTML = incomingRow.userText + " Lat: " +</p>
<p> incomingLat + " Lon: " +</p>
<p> incomingLong;</p>
<p> return incomingRow.userText;</p>
<p> }</p>
<p> function handleLocationError(error){</p>
<p> switch(error.code){</p>
<p> case 0:</p>
<p>updateGeolocationStatus("检索位置信息出错: " + error.message);</p>
<p>break;</p>
<p> case 1:</p>
<p>updateGeolocationStatus("用户阻止获取位置信息。");</p>
<p>break;</p>
<p> case 2:</p>
<p>updateGeolocationStatus("浏览器不能检测你的位置信息: " + error.message);</p>
<p>break;</p>
<p> case 3:</p>
<p>updateGeolocationStatus("浏览器检索位置信息超时。");</p>
<p>break;</p>
<p> }
}</p>
<p> </script></p>
<p></html>
