User guide

Configure Serial Port Settings
26 Chapter 1 Command Line Configuration Tasks
• When multiple clients share control of the serial port options, and a new
client opens a port, that new client might momentarily set the options to
default values before the application can set the options correctly. This
might momentarily disrupt communication with the other clients.
Depending on the operating system used by the client, it is possible to
set the default serial port options to match the options required by the
application. Then, there will be no disruption.
• When multiple clients share control of the serial-port options, some
serial-port options, such as case conversion, carriage return, newline
mapping, etc., might be handled on the client system. Therefore, these
options would apply to the client that set these options only.
• When the Digi device exclusively controls the serial port settings, any
attempt to change the serial port settings from a client will be silently
ignored. The client will believe the settings have been changed, when in
fact they have not. The only way to change the serial port settings is
through the command line on the Digi device or through the web UI.
• With reverse Telnet, reverse SSH, and connect, it is possible for a
single client machine to open a single shared port multiple times by
using multiple telnet or ssh sessions.
However, with RealPort, it is not possible for a single client machine to
open the same RealPort multiple times and use port sharing. Windows
simply prevents one machine from opening a RealPort more than once.
Unix does allow a single machine to open a RealPort more than once,
but the sharing is happening on that Unix machine, not on the Digi
device.
Unix sharing does merge data written to the port and shares control of
the port. However, it does not duplicate the incoming data to all
programs that have opened the same RealPort. Instead, the incoming
data is arbitrarily divided among the programs.
It is possible for one machine to use port sharing with RealPort, but only
by configuring the RealPort driver multiple times for the same Digi
device.
• Windows RealPort explicitly forces DTR and RTS to drop when it closes
a port. This could prevent other clients sharing that port from sending or
receiving data, depending on the configuration. If this is a problem, set
the shared port for exclusive control. Unix RealPort does not have this
problem.
Examples
The example "Display and change port-sharing settings" on page 199
shows how to use the “show sharing” and “set sharing” commands to
display current port-sharing settings, configure port-sharing settings, and
display the changed settings.