is a free open source Virtual serial port redirector
for Linux which supports the RFC-2217
COM Port Control Telnet extention, making it compatible
Server. The client creates a pseudo TTY port
in Linux, which redirects to a Terminal Server or a
Modem Server over a network. When used with NetModem
Server, it attaches to the next available modem in a
pool of modems, allowing linux applications dialout/dialin
access to the modem(s) over the network.
Cyclades-Serial-Client is included in software repositories
for many Linux distributions including Ubuntu, Fedora,
Debain, OpenSuse, Lucid, Mint, and Boss.
Installers are provided for both 32-bit and
By installing both Cyclades-Serial-Client and a modem
terminal emulator such as Minicom,
Linux users are provided dialout access to analog or
digital modems which are physically attached to a Windows
PC running NetModem Server. The modem server can manage
a pool of up to 256 modems, commonly 2, 4 or 8 modems
using standard RJ45 telephone connectors for smaller
applications, and up to 256 modems per server when using
T1 phone lines for enterprise applications.
can be downloaded and installed from most Linux software
repositories by using the following command line:
sudo apt-get install cyclades-serial-client
is needed to grant root access to the apt-get installer
program, and will prompt you for your administraor credentials.
will download and install the current available version
of cyclades-serial-client software from your configured
software repository. It will select the proper 32-bit
or 64-bit installer, matching the OS its installing
Cyclades-Serial-Client is installed, you can optionally
edit the configuration file named cyclades-devices
with a text editor.
To view the help file use: "man cyclades-devices".
The configuration file is usually located in /etc/,
so to edit the file using gedit you could use this command
sudo gedit /etc/cyclades-devices
cyclades-devices configuration file uses the following
= local device name, starting with a "/dev/"
rastype = "prts" or "path" can be
rasname = IP Address of the NetModem Server
physport = must be "1"
type = must be "rtelnet" for remote telnet
options = this can be left blank
is an example of a cyclades-devices configuration
The config is file can also contain comments, which
are lines beginning with a # character.
device names work best: /dev/ptypX where X is
a value between 0-9 or A-Z.
Any non-standard pseudo device name such as /dev/modem
can be used with Minicom, but such names may fail to
be accessible by some other serial communication applications.
Therefore we recommend using a valid pseudo device name
such as: /dev/ptyp0
The Client includes two executables:
- The virtual COM port redirector client
cyclades-serial-client - The client status/manager
The cyclades-serial-cli program is designed to
be run from init, so that is is loaded during boot up.
However doing so will cause it to continuously hold
one of the modems open in NetModem Server, so it is
recomended to run this from a terminal console instead
where it can easily be controlled (ie: stopped by pressing
Ctrl-C). This is done using the -x command line parameter
from a Terminal.
a Terminal and type the following command line:
sudo cyclades-ser-cli -p 5999 -m 1 -x /dev/ptyp0
Subsitute the above IP address with the actual IP
address (or hostname) of the NetModem Server PC.
most common parameters used are defined below:
-p 5999 [This must be one less then the NetModem
Server TCP Port]
-m 1 [Causes the client
to ignore the Carrier Detection signal]
the client to run in forground Console mode when started
from a Terminal]
/dev/ptyp0 [This overrides the device name in
the configuration file]
192.168.1.100 [The IP address (or hostname) of
the Modem Server]
should always be 1. A 0 setting will select TCP port
You should see the following:
client is now running, redirecting data between the
pseudo TTY named /dev/ptyp0 on the Linux box and a physical
modem device on the NetModem Modem Server software running
on a Windows PC.
The client also connects to the current Terminals pseudo
terminal device, usually named /dev/pts/1 or /dev/pts/2.
This is not a modem or serial device and should not
be used in Minicom.
It is important to use the -p parameter to specify
a value that is one less then the TCP port on the NetModem
Server. NetModem Server defaults to using TCP port
6000, in which case -p 5999 should always
be used in the client's command line.
It is also important to use the -m 1 parameter
to instruct the client to ignore the Device Carrier
Detection (commonly called the CD or DCD line). This
is due to a bug in cyclades-ser-cli that causes it to
detach the pseudo TTY from the telnet/socket connection
as soon as the modem server reports that the DCD line
is low(set to zero).
This prevents the applications from "hanging up"
or knowing when the modem has been disconnected, but
Minicom will still show the user a "NO CARRIER"
message to indicate the disconnection. A hangup can
be achived by closing/restarting cyclades-ser-cli .
Once the cyclades-serl-cli program is running, you can
optionally change the permissions of the pseudo TTY
port (virtual serial port) it creates, using the chmod
command from another Terminal or a script. This will
allow Minicom to access the port without needing to
elevate the users access using using Sudo when running
Minicom. For example:
chmod og=rw /dev/ptyp0
This gives everyone read and write access
to the named pseudo TTY device (a virtual serial port)
created by the client.
As with any serial device, only one user can open a
device at any given time. You can use multiple instances
of cyclades-serial-client to create additional pseudo
TTY devices so that other users or applications can
be connected to other modems/devices on the Server at
the same time, limited only to the number of shared
modems/devices on the Server.
To stop the client and to release the modem back
to the servers pool you can press Ctrl-C
in the cyclades-ser-cli Terminal window, or the
program can be sent a SIGTERM by any other means.
The cyclades-serial-client program is a client
status/manager tool which can monitor and control the
status of each cyclades-ser-cli that is defined in the
cyclades-devices file. However, this tool does not appear
to function with non cyclades devices.
The tool must be involked with one of the following
commands: start, stop, restart, or status, and
optionally a second parameter can be passed with the
specific device name to control such as /dev/ptyp0
or if the second parameter is not passed then the requested
action will be performed on all the devices defined
Cyclades-Serial-Client is an excellent tool, but lacks
some of the features of NetModem Client:
Cyclades-Serial-Client connecting to NetModem Server:
automated credential handling. If the modem server
requires user authentication, the user can manually
enter their username and password into Minicom.
support for multiple pools. The Cyclades-Serial-Client
will always connect to the first modem pool defined
in NetModem Server, on the next available COM port
found in this modem pool.
No SSL/TLS Encryption support. It may be possible
using SSLTunnel, but this is not suggested or supported
by PC Micro staff.
Carrier Detect (DCD) signal. This is due to a bug
in the current version of cyclades-ser-cli requiring
the -m 1 parameter to ignore this signal.
ability to connect to the modem on the server ONLY
while the pseudo TTY device is held open. This means
that one of the devices\modems on the NetModem Server
will be held open the entire time that cyclades-ser-cli
is running. Press Ctrl-C to exit cyclades-serl-cli
and release the modem device back to the NetModem
Server modem pool.