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COMET技术具体实现 结合PHP和JQUERY
具体看代码,费话不说
PHP服务端
$mem = new RTMEM();if(!$mem->conn()) exit(‘no mem server‘);if(!$mem->getstate()) exit(‘moonjksrv is not runing‘);$alminfo = $mem->get(‘alm_info‘);if(!$alminfo) exit(‘no alarm‘);$almobj = json_decode($alminfo);if(!$almobj) exit(‘no json data‘);$lastmodif = isset($_GET[‘timestamp‘]) ? $_GET[‘timestamp‘] : 0;$currentmodif = $almobj->timestamp;while ($currentmodif <= $lastmodif) // check if the data file has been modified{ usleep(1000000); // sleep 1 second to unload the CPU clearstatcache(); $alminfo = $mem->get(‘alm_info‘); if(!$alminfo) exit(‘no alarm‘); $almobj = json_decode($alminfo); if(!$almobj) exit(‘no json data‘); $currentmodif = $almobj->timestamp;}exit(json_encode($almobj));
以下是JS端
//comet ajax////var Comet = function(options){ this.init(options);};Comet.prototype = { constructor: Comet, init:function(options){ this.options = { url:"", callback:function(){} } this.options = $.extend(this.options,options||{}); this.url = this.options.url; this.callback = this.options.callback; this.timestamp = 0; this.noerror = true; this.lock = true; }, connect: function(){ this.lock = false; this.ajaxLoop(); }, disconnect: function(){ this.lock = true; }, ajaxLoop: function(){ if(this.url && !this.lock){ var _this = this; $.ajax({ url:_this.url, type:‘get‘, data:‘timestamp=‘ + _this.timestamp, dataType:‘json‘, cache:false, success:function(json){ _this.timestamp = json[‘timestamp‘]; _this.handleResponse(json); _this.noerror = true; }, complete:function(){ if (_this.noerror){ _this.ajaxLoop(); }else{ // if a connection problem occurs, try to reconnect each 1 seconds setTimeout(function(){_this.ajaxLoop()}, 1000); } _this.noerror = false; } }) } }, handleResponse: function(response){ this.callback(response); }, doRequest: function(request){ if(this.url && !this.lock){ $.get(this.url, { ‘msg‘: request } ); } }}/////// var comet = new Comet({ url:‘binsrv/rt_alm.php?type=getrtalm‘, callback:function(json){ //接收到数据的处理 if(typeof(page)!="undefined" && typeof(page.processAlmData)=="function") page.processAlmData(json); } }); comet.connect();
这样的话,服务器查询数据有更新才会返回AJAX请求,没有更新会直到超时(PHP默认30秒超时),这时COMET会重新连接
这样大大降低了频繁的AJAX请求,又没有降低实时性。
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