Oracle Database Discussions

Hello gurus ,

I am trying to connect database using telnet from windows machine ,
after login os , username ,password

i got $ prompt , after that i have given sqlplus command , then I have enter username,pwd correctly ,but I am unable to connect its giving error " Net service name is incorrectly specified ,

I have checked my tnsnames.ora file at the database system , i find all the entries are correct

plzzz can anybody help me .. how to connect database via telnet