502 Bad Gateway Error Through a Proxy

What the error means

The 502 code means that an intermediary server passed the request on and got an error or nothing at all. The intermediary may be our gateway, or it may be a server in front of the site itself.

In Prokso the gateway response looks like 502 NO_HOST_CONNECTION: the proxy could not connect to the site. If there is no name after the code, the 502 was returned by the site or its content delivery network.

Causes

• The site is down or overloaded. It does not answer anyone — neither through the proxy nor directly.
• The site rejected the connection from this address. The same site may answer from another address or another country.
• An error in the site address. A typo in the domain, a subdomain that does not exist, a wrong port.
• The protocol is mixed up. An HTTP request was sent to the SOCKS5 port or the other way round.
• A particular exit address is offline. In residential and mobile networks a device can drop off the network at any moment.

How to fix it

1. Retry the request: with rotation, the next one will go through a different address.
2. Check the site address and open it without the proxy — does it work at all?
3. Check the port and protocol: 823 is HTTP, 824 is SOCKS5.
4. Change the country or remove the city and ISP targeting.
5. On a sticky IP, change the session: take another port from the 10000–20000 range.
6. Add a retry on 502 with a short pause to your program — two or three attempts are enough.

How to check that it works

Test the line in the proxy checker. If the proxy responds and 502 remains on one site only, the cause is on that site's side.