Odd problem with rsh

[Oscar Levi <elf@buici.com>]

I have a UDB that has been running for months without trouble.  It
exchanges mail, acts as an ftp server, and is where I read mail.  I
upgraded slink as of Friday *and* I installed the 2.2.0 kernel.  It
runs a little faster.  But, it doesn't want to rsh to another host.

I cannot do the simple command:
  rsh -l <user> <remotehost> ls -a

I get the oddest error message:

  elf@hazel ~ > rsh -l elf florence ls -a
  select: protocol failure in circuit setup

Any ideas what this means?