6, in response to the HTTP protocol
Response structure format:
Response line (status line): HTTP version, status code, status message
Response header: Additional information message header, used by the client
Blank line: response header and the response between the entities necessary.
Response entity: text, examples of the information returned by the server to the browser:
Common HTTP response status code Meaning: HTTP status code of three decimal digits, the first status code defines the decimal number
The type, the latter two figures are not the role of classification. HTTP status code is divided into five types:
Common status codes: 200 OK // client request was successful
400 Bad Request // client requests a syntax error, it can not be understood by the server
401 Unauthorized // unauthorized request, the status code must be used with the WWW-Authenticate header field
403 Forbidden // server receives the request, but refused to provide services
404 Not Found // requested resource does not exist, eg: enter the wrong URL
Unexpected error 500 Internal Server Error // server occurs
503 Server Unavailable // server is currently unable to process the client's request, may return to normal after a period of time