Reptile foundation I

APP Generally, it encrypts itself ,HTTPS（http+SSL encryption ）, Attention to crawling by reptiles .

The client sends request To server , Server return response

REQUEST Part of the HTTP HEADER

charset： Decoding method , Prevent confusion code

Encoding： Some of them are compressed packages

User-Agent： Tell the server what client I am , Disguise as a browser to prevent anti crawling

Cookie： Login use , There are other functions .

login return setcookie,

because http Is stateless connection ,client Send to server http request , for the first time login, Send it again for the second time , The server still doesn't know client Who is it? .

In fact, for the first time login after , Server's response return setcookie, Equivalent to the server to client Assigned a id No. for identification .client After that, every time you send cookie add .

RESPONSE Of HTTP HEADER

Location： Indicate the jump link

Set-cookie：Userid

statuscode： Response status code ：2xx- success ,3xx- Jump ,4xx- Client error ,500- Server error .

300- Multiple available resources , Can be disposed of or discarded ;

301- Redirect ;

302- Redirect ;

304- Requested resource not updated , discarded .

python library , Such as urllib2 Redirect has been automatically skipped , Auto resend location Of request Return to code .