重新连接到服务器时如何强制 Atmosphere.js 使用首选传输？
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【中文标题】重新连接到服务器时如何强制 Atmosphere.js 使用首选传输？【英文标题】：How to force Atmosphere.js to use the preferred transport when reconnecting to the Server? 【发布时间】：2016-05-05 13:51:16 【问题描述】：当首选传输失败时，大气会尝试使用备用传输。它试图重新连接 maxReconnect 次数。之后它调用 onClose 和 onError。
当我再次尝试订阅时，Atmosphere 总是使用后备传输进行连接。
这是我的客户端配置：
AtmosphereRequestConfig jsonRequestConfig = // ...
jsonRequestConfig.setTransport(AtmosphereRequestConfig.Transport.WEBSOCKET);
jsonRequestConfig.setFallbackTransport(AtmosphereRequestConfig.Transport.LONG_POLLING);
jsonRequestConfig.setLogLevel("debug");
jsonRequestConfig.setMaxReconnectOnClose(1);
Atmosphere atmosphere = Atmosphere.create();
clientRequest = atmosphere.subscribe(jsonRequestConfig);
当我的服务器正在运行并且客户端第一次连接（页面重新加载）时，连接在 Websockets 上。然后我停止了我的服务器客户端显示：
atmosphere.js:3252 Sat Jan 30 2016 22:17:14 GMT+0100 (CET) Atmosphere: websocket.onclose
atmosphere.js:3252 Websocket closed, reason: Normal closure; the connection successfully completed whatever purpose for which it was created. - wasClean: true
atmosphere.js:3252 Sat Jan 30 2016 22:17:14 GMT+0100 (CET) Atmosphere: Firing onClose (closed case)
ConsoleLogger.java:32 AtmosphereListener: onClose
atmosphere.js:3252 Sat Jan 30 2016 22:17:14 GMT+0100 (CET) Atmosphere: Request already closed, not firing onClose (closed case)
atmosphere.js:3252 Sat Jan 30 2016 22:17:14 GMT+0100 (CET) Atmosphere: invoking .close() on WebSocket object
atmosphere.js:3252 Sat Jan 30 2016 22:17:14 GMT+0100 (CET) Atmosphere: Firing onReconnect
ConsoleLogger.java:32 AtmosphereListener: onReconnect
atmosphere.js:3252 Sat Jan 30 2016 22:17:14 GMT+0100 (CET) Atmosphere: Firing onReconnect
atmosphere.js:3252 Invoking executeWebSocket, using URL: ws://www.example.com:8080/socket/widget/2418C3F0-9A9B-48C4-8EE3-0541465EEACD%7C%7Crefdgdfgwe324234%7C%7CAF8F7A67-CDD0-4AD3-96C4-D447E970D0F8?X-Atmosphere-tracking-id=f89f00d8-b412-4825-80f9-ac8ca280edb5&X-Atmosphere-Framework=2.3.1-javascript&X-Atmosphere-Transport=websocket&Content-Type=application/json; charset=UTF-8&X-atmo-protocol=true
atmosphere.js:3252 Sat Jan 30 2016 22:17:14 GMT+0100 (CET) Atmosphere: websocket.onopen
atmosphere.js:3252 Websocket successfully opened
atmosphere.js:3252 Sat Jan 30 2016 22:17:15 GMT+0100 (CET) Atmosphere: websocket.onclose
atmosphere.js:3252 Websocket closed, reason: Connection was closed abnormally (that is, with no close frame being sent). - wasClean: false
atmosphere.js:3252 Sat Jan 30 2016 22:17:15 GMT+0100 (CET) Atmosphere: Request already closed, not firing onClose (closed case)
atmosphere.js:3252 Sat Jan 30 2016 22:17:15 GMT+0100 (CET) Atmosphere: Request already closed, not firing onClose (closed case)
atmosphere.js:3252 Sat Jan 30 2016 22:17:15 GMT+0100 (CET) Atmosphere: invoking .close() on WebSocket object
atmosphere.js:3252 Websocket reconnect maximum try reached 2
atmosphere.js:3252 Websocket error, reason:
atmosphere.js:3252 Sat Jan 30 2016 22:17:15 GMT+0100 (CET) Atmosphere: Firing onError, reasonPhrase: maxReconnectOnClose reached
然后我重新启动了我的服务器。客户端自动重新连接，因为他尝试在onError 中初始化大气连接。这是我得到的日志：
atmosphere.js:1195 WebSocket connection to 'ws://www.example.com:8080/socket/widget/2418C3F0-9A9B-48C4-8EE3-0541465EEACD%7C%7Crefdgdfgwe324234%7C%7CAF8F7A67-CDD0-4AD3-96C4-D447E970D0F8?X-Atmosphere-tracking-id=0&X-Atmosphere-Framework=2.3.1-javascript&X-Atmosphere-Transport=websocket&Content-Type=application/json;%20charset=UTF-8&X-atmo-protocol=true' failed: Error during WebSocket handshake: Unexpected response code: 302
atmosphere.js:3252 Sat Jan 30 2016 22:22:43 GMT+0100 (CET) Atmosphere: websocket.onerror
atmosphere.js:3252 Sat Jan 30 2016 22:22:43 GMT+0100 (CET) Atmosphere: websocket.onclose
atmosphere.js:3252 Websocket closed, reason: Connection was closed abnormally (that is, with no close frame being sent). - wasClean: false
atmosphere.js:3252 Sat Jan 30 2016 22:22:43 GMT+0100 (CET) Atmosphere: Firing onClose (closed case)
ConsoleLogger.java:32 AtmosphereListener: onClose
atmosphere.js:3252 Sat Jan 30 2016 22:22:43 GMT+0100 (CET) Atmosphere: Request already closed, not firing onClose (closed case)
atmosphere.js:3252 Websocket failed on first connection attempt. Downgrading to long-polling and resending
ConsoleLogger.java:32 AtmosphereListener: onTransportFailure: Websocket failed on first connection attempt. Downgrading to long-polling and resending
ConsoleLogger.java:32 AtmosphereListener: onTransportFailure: Websocket failed on first connection attempt. Downgrading to long-polling and resendingmhi_g$ @ ConsoleLogger.java:32Hgi_g$ @ SimpleConsoleLogHandler.java:36cgi_g$ @ Logger.java:262bgi_g$ @ Logger.java:250ugi_g$ @ Logger.java:178tgi_g$ @ Logger.java:162Agi_g$ @ Logger.java:129pNi_g$ @ AtmosphereListener.java:114(anonymous function) @ AtmosphereRequestConfig.java:389shc_g$ @ Impl.java:239vhc_g$ @ Impl.java:291(anonymous function) @ Impl.java:77_reconnectWithFallbackTransport @ atmosphere.js:1729_websocket.onclose @ atmosphere.js:1534
atmosphere.js:3252 Sat Jan 30 2016 22:22:43 GMT+0100 (CET) Atmosphere: ajaxRequest.onreadystatechange, new state: 2
2atmosphere.js:3252 Sat Jan 30 2016 22:22:43 GMT+0100 (CET) Atmosphere: ajaxRequest.onreadystatechange, new state: 3
atmosphere.js:2117 XHR finished loading: GET "http://www.example.com:8080/socket/widget/2418C3F0-9A9B-48C4-8…plication%2Fjson%3B%20charset%3DUTF-8&X-atmo-protocol=true&_=1454188963647"._executeRequest @ atmosphere.js:2117_execute @ atmosphere.js:644_reconnectWithFallbackTransport @ atmosphere.js:1745_websocket.onclose @ atmosphere.js:1534
atmosphere.js:3252 Sat Jan 30 2016 22:22:43 GMT+0100 (CET) Atmosphere: ajaxRequest.onreadystatechange, new state: 4
atmosphere.js:3252 Sat Jan 30 2016 22:22:43 GMT+0100 (CET) Atmosphere: ajaxRequest.onreadystatechange, new state: 2
atmosphere.js:3252 Sat Jan 30 2016 22:22:43 GMT+0100 (CET) Atmosphere: Firing onOpen
日志说：
第一次连接尝试时 Websocket 失败。降级为长轮询并重新发送
如何在服务器重启时强制 Atmosphere.js 使用首选传输 (Websockets) 而不是备用传输 (Long Polling)？
【问题讨论】：
【参考方案1】：如何在服务器重新启动时强制 Atmosphere.js 使用首选传输 (Websockets) 而不是回退传输 (Long Polling)？
Atmosphere 客户端自动尝试使用fallbackTransport 重新连接。这是默认行为。
要强制它使用首选传输重新连接，您可能必须更改默认行为。
可以通过在大气.js see here 中注释掉这一行来改变这一点。
这将确保在重新连接时始终使用首选的 web-socket 传输，并且不会使用fallbackTransport。
_websocket.onclose = function(webSocketOpened) //... if (_abortingConnection) atmosphere.util.log(_request.logLevel, ["Websocket closed normally"]); /** remove if you never want to use fallback transport else if (!webSocketOpened) _reconnectWithFallbackTransport("Websocket failed on first connection attempt. Downgrading to " + _request.fallbackTransport + " and resending"); */ else if (_request.reconnect && _response.transport === 'websocket' ) _clearState(); if (_requestCount++ < _request.maxReconnectOnClose) _open('re-connecting', _request.transport, _request); if (_request.reconnectInterval > 0) _request.reconnectId = setTimeout(function () _response.responseBody = ""; _response.messages = []; _executeWebSocket(true); , _request.reconnectInterval); else _response.responseBody = ""; _response.messages = []; _executeWebSocket(true); else atmosphere.util.log(_request.logLevel, ["Websocket reconnect maximum try reached " + _requestCount]); if (_canLog('warn')) atmosphere.util.warn("Websocket error, reason: " + message.reason); _onError(0, "maxReconnectOnClose reached");
另一种方法是使用onReconnect 回调动态切换回clientRequest.request 参数。
为什么？
因为当连接关闭并调用onTransportFailure 时。 Atmosphere 将传输更改为 fallbackTransport 并且最终可能以 = 'none' 结束（如果它设置为 websocket）。
假设您的请求包括以下配置：
request.reconnectOnServerError= true, request.executeCallbackBeforeReconnect= true;
您可以将此添加到您的 onReconnect 回调中：
clientRequest.request.transport = 'websocket'; // force preferred transport on reconnect //clientRequest.request.fallbackTransport = 'websocket'; // optional
问题是，如果您将回退设置为websocket，它只会尝试重新连接一次，就好像您将其留空一样，如果您使用了url（以ws:// 开头，它仍将使用web-socket 协议或wss://) 而不是webSocketUrl。
request.url = 'ws://example.com/ws';
【讨论】：
这有什么帮助？ 能否再写一点解释。 嗯，它并没有真正的帮助。您应该记住，对于仅提供长轮询的客户端，它应该仍然有效。如果它通过长轮询连接，它应该检查 Websockets 是否可用并尽可能升级。 任何合适的解决方案？以上是关于重新连接到服务器时如何强制 Atmosphere.js 使用首选传输？的主要内容，如果未能解决你的问题，请参考以下文章