webSocket_websocket连接_websocket与socket区别(2)

连接时若超时切换协议的代码

while(1) {
        var protocol = that.protocol = that._protocols.shift();
        if (!protocol) {
            return false;
        }
        // Some protocols require access to `body`, what if were in
        // the `head`?
        if (SockJS[protocol] &&
            SockJS[protocol].need_body === true &&
            (!_document.body ||
             (typeof _document.readyState !== 'undefined'
              && _document.readyState !== 'complete'))) {
            that._protocols.unshift(protocol);
            that.protocol = 'waiting-for-load';
            utils.attachEvent('load', function(){
                that._try_next_protocol();
            });
            return true;
        }
//下面的to = 就是计算连接超时时间的，调用delay，在连接超时时关闭这个协议的连接。
        if (!SockJS[protocol] ||
              !SockJS[protocol].enabled(that._options)) {
            that._debug('Skipping transport:', protocol);
        } else {
            var roundTrips = SockJS[protocol].roundTrips || 1;
            var to = ((that._options.rto || 0) * roundTrips) || 5000;
            that._transport_tref = utils.delay(to, function() {
                if (that.readyState === SockJS.CONNECTING) {
                    // I can't understand how it is possible to run
                    // this timer, when the state is CLOSED, but
                    // apparently in IE everythin is possible.
                    that._didClose(2007, "Transport timeouted");
                }
            });

            var connid = utils.random_string(8);
            var trans_url = that._base_url + '/' + that._server + '/' + connid;
            that._debug('Opening transport:', protocol, ' url:'+trans_url,
                        ' RTO:'+that._options.rto);
            that._transport = new SockJS[protocol](that, trans_url,
                                                   that._base_url);
            return true;
        }
    }

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