HTTP 101 Switching Protocols vs 521 Web Server Is Down
HTTP 101 (Switching Protocols) is a 1xx Informational response, while 521 (Web Server Is Down) is a 5xx Server Error response. 101 indicates that the server understands the Upgrade header field request and indicates which protocol it is switching to. In contrast, 521 means that cloudflare-specific. The origin server refused the connection.
설명
The server understands the Upgrade header field request and indicates which protocol it is switching to.
이 코드를 보게 되는 경우
When upgrading from HTTP/1.1 to WebSocket, or to HTTP/2.
해결 방법
This is normal behavior during protocol upgrades. Ensure your client supports the target protocol.
설명
Cloudflare-specific. The origin server refused the connection.
이 코드를 보게 되는 경우
When Cloudflare can't establish a TCP connection to the origin server.
해결 방법
Check that the origin server is running and the firewall allows Cloudflare IPs.
주요 차이점
101 is a 1xx Informational response, while 521 is a 5xx Server Error response.
HTTP 101: The server understands the Upgrade header field request and indicates which protocol it is switching to.
HTTP 521: Cloudflare-specific. The origin server refused the connection.
You encounter 101 when when upgrading from HTTP/1.1 to WebSocket, or to HTTP/2.
You encounter 521 when when Cloudflare can't establish a TCP connection to the origin server.
언제 어떤 것을 사용할지
For 101 (Switching Protocols): This is normal behavior during protocol upgrades. Ensure your client supports the target protocol. For 521 (Web Server Is Down): Check that the origin server is running and the firewall allows Cloudflare IPs.