proxyip probe

GET  /ip[?n=1&tries=36&format=json]   live-probe, return usable proxyip(s) for YOUR vantage
GET  /check?ip=1.2.3.4[:port][&sni=domain]
POST /batch  {"ips":["1.2.3.4:443",...],"sni":"optional"}  (max 16)
candidates embedded: 258