Status-Code
- 1xx: Informational - Request received, continuing process
- 2xx: Success - The action was successfully received,
understood, and accepted
- 3xx: Redirection - Further action must be taken in order to
complete the request
- 4xx: Client Error - The request contains bad syntax or cannot
be fulfilled
- 5xx: Server Error - The server failed to fulfill an apparently
valid request
Status-Code = Status-text
"100" : Continue
| "101" : Switching Protocols
| "200" : OK
| "201" : Created
| "202" : Accepted
| "203" : Non-Authoritative Information
| "204" : No Content
| "205" : Reset Content
| "206" : Partial Content
| "300" : Multiple Choices
| "301" : Moved Permanently
| "302" : Found
| "303" : See Other
| "304" : Not Modified
| "305" : Use Proxy
| "307" : Temporary Redirect
| "400" : Bad Request
| "401" : Unauthorized
| "402" : Payment Required
| "403" : Forbidden
| "404" : Not Found
| "405" : Method Not Allowed
| "406" : Not Acceptable
| "407" : Proxy Authentication Required
| "408" : Request Time-out
| "409" : Conflict
| "410" : Gone
| "411" : Length Required
| "412" : Precondition Failed
| "413" : Request Entity Too Large
| "414" : Request-URI Too Large
| "415" : Unsupported Media Type
| "416" : Requested range not satisfiable
| "417" : Expectation Failed
| "500" : Internal Server Error
| "501" : Not Implemented
| "502" : Bad Gateway
| "503" : Service Unavailable
| "504" : Gateway Time-out
| "505" : HTTP Version not supported
详情：https://tools.ietf.org/html/rfc2616#section-10.1.1
