You need to run bootparamd (not the same as bootpd) on the server.

TechSupp writes:
 >   Anyhow, if I recall rightly, this is a new one on me....I'm attempting
 > NFS installing, and the tftp'ing of the netboot program goes fine, but
 > something's spooked the bootpd into this;
 > 
 >   net_open: client addr: 192.168.1.12        <--this is right
 >   netif_get: timeout; resetting
 >   netif_get: timeout; resetting
 >   netif_get: timeout; resetting
 >   bootparamd: 'whoami' call failed
 >   net_open: bootparam/whoami RPC failed
 >   boot: netbsd: input/output error
 >   boot: