HTTP HTTP GET HTTP replaced headers CURLOPT_TIMECONDITION If-Modified-Since # Server-side HTTP/1.1 503 Error Date: Thu, 11 Jul 2019 02:26:59 GMT Server: test-server/swsclose Retry-After: 22 # Client-side http HTTP Retry-After header parsing and extraction lib1594 http://%HOSTIP:%HTTPPORT/1594 ^User-Agent:.* GET /1594 HTTP/1.1 Host: %HOSTIP:%HTTPPORT Accept: */* Retry-After: 22