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Troubleshooting

"Empty reply from server" on ISP and datacenter proxies

curl: (52) Empty reply from server is how a static proxy says no. A wrong password, a blocked port and a restricted target all end the same way, with the connection closed and no error code, and that is deliberate: a proxy that answers 407 or 403 tells scanners it is a proxy and gets the IP flagged on the sites you bought it for.

Written By Carmine Cella

Last updated 1 day ago

curl: (52) Empty reply from server is how a static proxy says no. A wrong password, a blocked port and a restricted target all end the same way, with the connection closed and no error code, and that is deliberate: a proxy that answers 407 or 403 tells scanners it is a proxy and gets the IP flagged on the sites you bought it for.

Diagnose from your side, in this order

You seeCheck
Empty reply on every requestThe credentials. Open ISP Proxies, click View on the plan and copy the line again: each IP has its own username and password, and Reset Password changes them. If IP authentication is on (Settings → Auth), check that the address you connect from is on the list; your office IP may have changed.
Empty reply on one site onlyThe target is on the restricted list (government sites, banks, and others). Verified accounts can ask for access; see the acceptable use article.
Empty reply on one port onlyThe port is blocked by default: mail ports 25, 110, 143, 465, 587, 993, 995 and a few others. Lifting a port restriction needs KYC and approval.
Connection timed out insteadThe plan has expired, or the IP was replaced. Check the Status column under Your Plans and open View for the current list.
The target blocks or challenges you with a pageThe proxy works; the site has its own rules for that IP. Replace the IP from Settings → Replace, or move that target to the Unlocker API.
ISP Proxies, Proxy list: the Format selector, the line for each IP, and Download and Copy

A quick test

curl --proxy http://USERNAME:PASSWORD@203.0.113.45:23503 https://ipinfo.io/json

If this returns JSON with the proxy's own address as ip, the proxy is fine and the problem is specific to your target or port.

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