When using cu
you may see
Device Busy error messages.
This means that some other process is using the device
you wish to use.
This frequently occurs when you change device characteristics
and quickly dial.
This is because ttymon owns the device
for a short period and the device
is busy while ttymon owns it.
Wait 30 seconds, then retry your dial request.
Device Busy message may also indicate
that the device is already being used
to dial out of (or into) your system.
In this case,
wait a few minutes, then retry your dial request.
Sometimes you can have a setup you know works properly, but you get no answer when dialing in. The most common cause for this condition is that someone else just finished dialing out, and ttymon is busy resetting the line and the modem for the next call. Wait one minute, then retry your dial request.
Sometimes you'll be able to reach a system over both TCP/IP and serial lines. This happens when the system is specified in both the /etc/uucp/Systems file and in the /etc/uucp/Systems.tcp file. When this occurs, BNU usually chooses the TCP/IP connection.
You can edit the /etc/uucp/Sysfiles file to force BNU to use the serial connection. See Sysfiles(4bnu) for more information.