I am behind a proxy server in my college. It uses a simple username and password authentication. And i connect to the proxy server to port 3128. now i want to telnet simply to say any website on the internet like$ telnet www.google.com 80this gives me error telnet: could not resolve www.udacity.com/80: Name or service not knownHow can I define the proxy settings for telnet? I have already set environment variables http_proxy and HTTP_PROXY. Also have applied system wide proxy. 
How to telnet via proxy authentication?
authentication;proxy;telnet
You can use Proxychains for this.First install proxychains, using the command:$ apt-get install proxychainsThen configure your proxy settings in /etc/proxychains.conf file.Add at last, these lines for HTTP and HTTPS proxy.http    proxy-ip   proxy-port    username        passwordhttps   proxy-ip   proxy-port    username        passwordNow you can do telnet by using the following command:$ proxychains telnet www.google.com 80