Typically, HTTP is an unreliableprotocol to use for delivering Web service messages.
通常,HTTP 不是用于传递 Web 服务消息的可靠协议。
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The CometD framework is an implementation of the Bayeux protocol, which allows for a multi-channel asynchronous communication stream over unreliable networks between a client and server.
Transport protocol: data services could be consumed via reliable (such as JMS via MQ Series) or unreliable transport messaging protocols (such as HTTP).