simulate connection with netcat

Hello,

my long-term intention is to write a cross-platform GUI-authpf-client
without using libssh or libssh2. Before I get into that I'd like to simulate
the ssh-connection/authentication via netcat.
I took a look at the RFCs but don't get it working.

% nc 127.0.0.1 22
SSH-2.0-OpenSSH_5.2
SSH-2.0-OpenSSH_5.2 <-- entered by me
... a lot of text ...

What do I enter now to authenticate?
My attempts resulted in "Packet corrupt".

regards,
jake