I have many big lists of free proxies on text files. I need to write a small program which can test these proxies if they work or not. To do that i need to send ping on each proxy, but this is not a 100% solution because many proxies block ping. So someone tell me to use "extended ping" mathod. With this method i will be able to send to any site a ping using a proxy. So i can understand if the proxy is alive. After i found the alive proxies, can Java set them as system(operation system's) default proxy? Is this possible on latest version of SunJava for Linux and Windows?