If you have a firm understanding of sockets, its completly simplistic to connect. You said you used telnet to connect. Well, connect a socket, and send the exact same commands you used with telnet, thorugh your program. You know you need a USER with flags, then along with the NICK. From there, replying to a PING server is easy, just attack what follows the ping to a PONG responce. Fairly simple.
I'm not too into c\c++ sockets, but I've done one in C# and works fairly easy. If you need help with what all the commands mean, i would suggesting hitting google up for
"irc rfc".
