Programming Cloud Services for Android handheld Systems/coursera notes

1.Introduction

Google + Microsoft has 1000,000+ servers to support their services, such as Google\bing\gmail and so on

Course Objective: How to establish a secure, upgradeable (scalable, security) service and mobile communication

2.Communication protocols

Select a protocol ("language") between a device and the cloud, which specifies a set of rules ("language syntax"), and the choice of a protocol directly relates to the security, reliability, Speed (security\reliable\quickly) of the WebService, which specifies the syntax, semantics , Time (syntax\semantic\timing)

3.Intro to HTTP

The HTTP protocol is a CLIENT-SERVER protocol that requests a resource (resources) on the server, and a server feedback (Response) response. HTTP is a basic protocol and will be discussed in the next course webscoket.

Webscoket principle of the following from the Baidu Encyclopedia:

WebSocket protocol is HTML5 a new protocol (protocol). It is the implementation of browser-to-server full-duplex communication (Full-duplex). Many web sites are being polled (polling) in order to achieve instant messaging (real-time). Polling is at a specific interval (time interval) (for example, every 1 seconds), the browser sends an HTTP request to the server, and the server returns the latest data to the client's browser. This traditional HTTP request pattern brings with it the obvious drawback that the browser needs to constantly make requests to the server (request), but the header of the HTTP request is very long, and the data contained in it may be a small value, which can consume a lot of bandwidth.

in the WebSocket API, browsers and servers only need to do a handshake, and then a fast channel is formed between the browser and the server. The data can be transmitted to each other directly between the two. corresponding link: http://www.ibm.com/developerworks/cn/web/1112_huangxa_websocket/back to the course, the client that initiates the request always receives the service side. Mobile app, browser, everything can be a client. Choose its reason: infrastructure perfect so much infrastructure, code complete a better understanding, multiplexing convenient reuse, Common Interface. 4.Why HTTP?

... Cond