Web Note 01-1

Http:url:

Full name is uniform Resource Locator (Uniform Resource Locator)

With 1 URLs, you can find only one resource on the Internet

Each resource has a unique URL

URL format:

Basic format: Protocol header://Host address/path

Protocol header: Different protocols, which represent different resource lookup and transmission methods. such as HTTP,AFP, etc.

Host address: The IP address (domain name) where the resource host resides

Path: The specific location of each resource at the host address

HTTP protocol:

The full name of HTTP is Hypertext Transfer Protocol, Hypertext Transfer Protocol

Specifies the format of data transfer between the client and server

Enables client and server to communicate data

HTTP protocol is the most extensive protocol in network programming

Features of the HTTP protocol

1, fast and simple: because the HTTP protocol is simple, so the HTTP server program size is small, fast communication speed

2, Flexible: HTTP allows the transfer of any type of data

3, HTTP 0.9 and 1.0 use a non-persistent connection: limit each connection to only one request, the server immediately after the client's request to disconnect, this way can save transmission time

4, HTTP 1.1 uses persistent connection: You do not have to create a new connection for each Web object, and one connection can transfer multiple objects

HTTP Communication Process Request

HTTP protocol: A completed client to the server HTTP strange request, to include the following content

Request Line: Specify request method, request resource path, and HTTP protocol version #表示访问根目录 # get/http/1.1

Request Header: Information about the client's environment, the host address requested by the client, etc.

The request header contains at least: #客户端要访问的服务器主机的地址 # host:m.baidu.com

The request header can also contain the following information:

#客户端的类型, client Software Environment # User-agent:iphone AppleWebKit

#客户端能接受的数据类型 # accept:text/html

#客户端的语言环境 #accept-language:zh-cn

#客户端支持的数据压缩格式 # Accept-encoding:gzip

#访问结束后, whether the connection is disconnected # Connection:close

Request Body (optional): Specific data that the client sends to the server, such as the file data to be uploaded

Format: At the end of each request message, use \ r \ n, after the last request, add \ r \ n (that is, the last request message is \r\n\r\n);

Response

The HTTP protocol stipulates that a full HTTP response should contain the following content

Status line: Contains the HTTP protocol version, status code, status English name

#请求成功 http/1.1 OK Status Code 200 starts with a successful

Response header: Contains a description of the server, a description of the returned data

#服务器类型 Server ...

#返回数据的类型 Contect-type:

#返回数据的长度 Contect-length:

#反应时间 Date ...

#ETag (hash value): ETA.G: "xxxxxxx";

Entity content: The specific binary data that the server returns to the client

* The status line and the response header are for the developer to debug, the entity content is for the user to see

Development scenarios

Apple officially offers three options

1, the introduction of nsurlconnection:ios2.0, the use of simple, the oldest and most direct one of the program

2, Nsurlsecssion:ios7 launch, more powerful function than nsurlconnection

3, the bottom of cfnetwork:nsurl, pure C language, almost no

Third-party frameworks

ASIHTTPRequest: Cfnetwork nickname HTTP Terminator for the underlying, extremely powerful, 2012 stop update, based on MRC

Afnetworking: The bottom layer for the nsurlconnection&nsurlsecssion simple and easy to use, to achieve basic functions, maintenance and use of many people

Mknetworkkit: Low-level for nsurlconnection easy to use, maintenance and usage of less people

Alamofire: The bottom layer for nsurlsession based on Swift lightweight development, features far less than afnetworking

Nsurlconnection steps

1. Nsurl: Determine which resources to access

2, Nsurlrequest: According to the URL resume request, to the server request data

3, Nsurlconnertion: Establish a network connection, say the request (asynchronous) sent to the server

eg

1. Create the resources you want to access

Nsurl *url=[nsurl urlwithstring:@ "http://m.baidu.com"];

2. Requesting data from the server

Nsurlrequest *request=[nsurlrequest Requestwithurl:url];

3. Establish a network connection

[Nsurlconnection sendasynchronousrequest:request queue:[nsoperationqueue Mainqueue] completionHandler:^ ( Nsurlresponse *response,nsdata *data, Nserror *connectionerror) {

NSLog (@ "%@", data);

}];

Nsurlconnection Summary:

Sendasynchronousrequest: This method is asynchronous suffocation, and the programmer does not have to consider whether to thread or create the queue, which will send the previously built request to the server asynchronously. Wait until the server response is received, and the queue is responsible for dispatching the Comloetionhandler

Queue

Scheduling Completionhandler Execution of queues

[[Nsoperationqueue alloc]init], background thread executes asynchronously

[Nsoperationqueue Mainqueue], the main thread executes asynchronously

Selection of queues:

Select New queue scheduling if you want to take time-consuming processing of data, such as decompression compression, etc.

If you simply want to handle it, update the UI now and select the Home column

Completionhandler

Network access is over, callback method after receiving response data to the server

Response, the response of the server, which is usually called when the download function is developed

Response Property Description:

URL server Feedback URL, sometimes the server will redirect the new URL

The MIMEType server tells the client that the binary data type is returned, and ContentType knows what software to use to process the returned data based on the MIMEType client.

StatusCode Status code: 1XX message 2XX Success 3XX more Select 4XX Client error 5XX Server error

Expectedcontentlength data length, download file total length

Suggestedfilename Recommended file name

The binary data returned by the data server and what the programmer cares about most

Connectionerror connection error, any network access error may occur

Request Brief

Create a request based on a URL

Set request properties: Cache policy, Network timeout market

Tell the server about additional information: client type, authentication, etc...

[Request setvalue:@ "IPhone AppleWebKit" forkey:@ "user-agent"];

Web Note 01-1