The communication between your program and the irc server can be done with Winsock. Search vb-world for articles/examples on Winsock.

How the irc protocol works:
ftp://ftp.isi.edu/in-notes/rfc1459.txt
ftp://ftp.isi.edu/in-notes/rfc2810.txt
ftp://ftp.isi.edu/in-notes/rfc2811.txt
ftp://ftp.isi.edu/in-notes/rfc2812.txt
ftp://ftp.isi.edu/in-notes/rfc2813.txt