新 HTTP 状态码详解程序员

起因是同学发起的一个请求被乌云返回了 520 ，遂查一下新增的 HTTP 状态码

CloudFlare 
 
CloudFlare's reverse proxy service expands the 5xx error space to signal issues with the origin server. 
 
520 Unknown Error 
 
The 520 error is used as a "catch-all response for when the origin server returns something unexpected", listing connection resets, large headers, and empty or invalid responses as common triggers. 
 
521 Web Server Is Down 
 
The origin server has refused the connection from CloudFlare. 
 
522 Connection Timed Out 
 
CloudFlare could not negotiate a TCP handshake with the origin server. 
 
523 Origin Is Unreachable 
 
CloudFlare could not reach the origin server; for example, if the DNS records for the origin server are incorrect. 
 
524 A Timeout Occurred 
 
CloudFlare was able to complete a TCP connection to the origin server, but did not receive a timely HTTP response. 
 
525 SSL Handshake Failed 
 
CloudFlare could not negotiate a SSL/TLS handshake with the origin server. 
 
526 Invalid SSL Certificate 
 
CloudFlare could not validate the SSL/TLS certificate that the origin server presented.

520 – 未知错误
520 错误包含了原始服务器返回意外响应的全部问题
520 常由以下原因引起：

• 连接重置
• Headers 超过标头大小限制（超过 8KB）
• 空的响应来源
• 无效的 HTTP 响应
• HTTP 响应缺少响应标头

521 – Web 服务器已关闭
源服务器拒绝了云服务器的连接

522 – 连接超时
云服务器没有和源服务器完成 TCP 握手

523 – 源头不可达
云服务器无法到达原始服务器，可能是源服务器的 DNS 记录不正确

524 – 超时
云服务器可以完成 TCP 握手，但是没有及时收到 HTTP 响应

525 – SSL 握手失败
云服务器不能完成与原始服务器的 SSL/TLS 握手

526- 无效的 SSL 证书
云服务器无法验证原始服务器的 SSL 证书

nginx 
 
The nginx web server software expands the 4xx error space to signal issues with the client's request. 
 
444 No Response 
 
Used to indicate that the server has returned no information to the client and closed the connection. 
 
495 SSL Certificate Error 
 
An expansion of the 400 Bad Request response code, used when the client has provided an invalid client certificate. 
 
496 SSL Certificate Required 
 
An expansion of the 400 Bad Request response code, used when a client certificate is required but not provided. 
 
497 HTTP Request Sent to HTTPS Port 
 
An expansion of the 400 Bad Request response code, used when the client has made a HTTP request to a port listening for HTTPS requests. 
 
499 Client Closed Request 
 
Used when the client has closed the request before the server could send a response.

Nginx 拓展了 4xx 错误代码
444 – 没有响应
服务器没有返回响应，并且关闭了连接

495 – SSL 证书错误
客户端提供了一个无效的证书时返回 400 错误码的扩展

496 – 需要 SSL 验证
需要客户端提供 SSL 证书，客户端却没有提供返回 400 错误码的扩展

497 – HTTP 请求发送到了 HTTPS 端口
当客户端把一个 HTTP 请求发送到了 HTTPS 端口时返回 400 错误码的扩展

499 – 客户端关闭请求
在服务器发送响应之前客户端就关闭了连接

The Internet Information Services expands the 4xx error space to signal errors with the client's request. 
 
440 Login Timeout 
 
The client's session has expired and must log in again. 
 
449 Retry With 
 
The server cannot honour the request because the user has not provided the required information. 
 
451 Redirect 
 
Used in Exchange ActiveSync when either a more efficient server is available or the server cannot access the users' mailbox. The client is expected to re-run the HTTP AutoDiscover operation to find a more appropriate server.

440 – 登录超时
客户端的会话已经过期，必须重新登录

449 – 重试
客户端没有提供所需要的信息，服务器不能正确响应

451 – 重定向
在使用 Exchange ActiveSync 时不能访问用户的邮箱时，需要重新运行 HTTP 自动发现 来找到更合适的服务器

原文链接：维基百科 – HTTP状态码