New Post: Create an SSH tunnel

ForwardedPortLocal != ForwardedPortDynamic

From ssh man-page:

     -D [bind_address:]port
             Specifies a local ``dynamic'' application-level port forwarding.

Else the code looks fine.

Edit: On a second glance... Your Readkey() should be inside the using-block, or?
Else client would be disposed and disconnected after the forwarding started.