webSocket_websocket连接_websocket与socket区别(3)

观察上面报错信息中的uri：uri=http://xxx/user/854/qckzogtf/xhr_streaming;因为正常情况下连接为websocket连接，这个uri应该为ws=http://xxx/user/854/qckzogtf/websocket，由此可见，这里应该是切换为xhr_streaming协议了

前面也说过，他们网络环境较慢，所以才想，应该是连接超时导致的，有上面可知，to为超时时间，计算公式为

var to = ((that._options.rto || 0) * roundTrips) || 5000;

关键在于that._options.rto，这个是new的时候的设置项，所以可以设置rto超时长一点。websocket连接

结果发现设置中只有

that._options = {devel: false, debug: false, protocols_whitelist: [],info: undefined, rtt: undefined};

这几项，并没有rto，于是继续看

var SockJS = function(url, dep_protocols_whitelist, options) {
    if (this === _window) {
        // makes `new` optional
        return new SockJS(url, dep_protocols_whitelist, options);
    }
    
    var that = this, protocols_whitelist;
    that._options = {devel: false, debug: false, protocols_whitelist: [],
                     info: undefined, rtt: undefined};
    if (options) {
        utils.objectExtend(that._options, options);
    }
    that._base_url = utils.amendUrl(url);
    that._server = that._options.server || utils.random_number_string(1000);
    if (that._options.protocols_whitelist &&
        that._options.protocols_whitelist.length) {
        protocols_whitelist = that._options.protocols_whitelist;
    } else {
        // Deprecated API
        if (typeof dep_protocols_whitelist === 'string' &&
            dep_protocols_whitelist.length > 0) {
            protocols_whitelist = [dep_protocols_whitelist];
        } else if (utils.isArray(dep_protocols_whitelist)) {
            protocols_whitelist = dep_protocols_whitelist
        } else {
            protocols_whitelist = null;
        }
        if (protocols_whitelist) {
            that._debug('Deprecated API: Use "protocols_whitelist" option ' +
                        'instead of supplying protocol list as a second ' +
                        'parameter to SockJS constructor.');
        }
    }
    that._protocols = [];
    that.protocol = null;
    that.readyState = SockJS.CONNECTING;
    that._ir = createInfoReceiver(that._base_url);
    that._ir.onfinish = function(info, rtt) {
        that._ir = null;
        if (info) {
            if (that._options.info) {
                // Override if user supplies the option
                info = utils.objectExtend(info, that._options.info);
            }
            if (that._options.rtt) {
                rtt = that._options.rtt;
            }
            that._applyInfo(info, rtt, protocols_whitelist);
            that._didClose();
        } else {
            that._didClose(1002, 'Can\'t connect to server', true);
        }
    };
};

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