502 Bad Gateway refers to a wrong gateway or an invalid gateway; it represents a network error on the Internet. Displayed in the page feedback given in the WEB browser.
Meaning: This usually does not mean that the upstream server is down (unresponsive gateway/proxy), but rather that the upstream server and gateway/proxy do not agree on a protocol for exchanging data. Given that the Internet protocol is fairly well understood, it often means that one or two machines have been incorrectly or incompletely programmed.
The rescue method: Refresh. The principle of refresh: Many people may not know that there are two types of refresh. The so-called refresh actually means downloading data from the server to the local memory or hard disk buffer, and then reading the data from the local memory or hard disk to the browser for display to us.
1. Basic refresh: just click refresh or use the F5 shortcut key. A basic refresh may only re-fetch data from the local hard disk to the browser, and may not necessarily re-send a request to the server. Most users refresh like this most of the time, and it has no effect if they encounter a 502 error.
2. Refresh from the server: If you directly click on the web link you want to browse again, you will find that the page showing the "502 bad gateway" error message can be browsed normally after clicking the link. The solution is to refresh from the server: shortcut key ctrl F5, which means re-sending the request to the server.
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