Kernel debugging with Windbg

I'm trying to set up a kernel debugging session with Windbg.  On the target system I added /Debugport=com1 to boot.ini, and I get the target session started easily with "windbg -k".  By using a simple serial reader program on the host I can see that windbg on the target is sending a packet of bytes periodically, that is being received on the host.  But I can't figure out how to start windbg on the host so it attaches to the target.  All the Windbg documentation I can find only talks about connecting the host using 'npipe:xxxx' or 'tcp:xxx', but I need to connect over the serial port.  Does anyone know how to get the host started and attached over the com1 port?

Thanks much...

 -steve