[marjan]

here is the problem: guessing both username and password via bruteforce would take too much time. if we take in account the network latency the time needed increase drastically
in either case take a look at the rfc 1928 and implement the sock5 protocol, or just search for any library online that you can already use, then during the authentication just send whatever username and password you want and see the response packet for confirmation (if server send any, i didnt bothered reading the rfc for you)