The other answerers are correct that the networking
stack isn't functional in single user mode; however,
there is something similar that you might consider.
In many server rooms, it's common to install a terminal
concentrator that connects to the serial ports of
multiple machines. In that situation, you "telnet"
to the terminal concentrator and open the connection
to the serial port of the machine in question. If
the console has been redirected to the serial port,
then you're in business.
A similar solution which avoids the need for a terminal
concentrator is to connect the serial port of a machine
to the serial port of a second machine via a
cross-over RS232 cable. Then you can "tip" from one
machine to the other.
Finally, on newer machines (well, typically "servers"),
it's becoming common for there to be a "service processor"
to provide "LOM" (lights out management). If this
is available, you telnet to the service processor (which
has a distinct IP address from the rest of the system)
and it will have the capability to take over the
console.
Not sure if this answers your question, but it seemed
like it might be related to the problem you might be
trying to solve.