Publisher: PC Micro Systems, Inc.
Thousand Oaks, California, USA
Table of Contents
1. Overview of NetDialOut & Modem Pooling
NetDialOut is COM port redirector software for Windows, which allows
applications to access networked device servers that provide remote
modems or other serial devices.
Device servers that provide remote modems over a network are commonly
known as a modem server, a modem pooling device, a universal gateway,
or a Network Access Server (NAS).
NetDialOut is designed for all servers that support the COM Port Control
(RFC-2217) extention to the telnet protocol. This includes Cisco Access
Servers, Cisco Routers with analog modem modules, and Cisco Routers
with PVDM digital modem modules. It also works with modem servers from
many other manufactures that support COM Port Control.
PC Micro also publishes two other COM port redirector products: NetSerial
NetSerial is a universal COM port redirector which supports
nearly all TCP compatible device servers. It also includes a virtual
modem emulator allowing modem based software to be redirected to telnet
servers or device servers. NetSerial also allows Cisco equipment to
be used for both Dial-Out and Dial-In applications. NetSerial can be
downloaded from: https://pcmicro.com/netserial
NetModem Server turns a Windows PC into a Modem Server, and the
includes free Client redirector software for all your Windows PC's.
The free NetModem Client redirector is nearly identical to the NetDialOut
redirector, but is limited to only allowing connections to NetModem
Server(s). NetModem can be downloaded from: https://pcmicro.com/netmodem
NetDialOut was created as an alternative to the "Cisco DialOut
Utility" for Windows 95/98 software from Cisco Systems, Inc.
NetDialOut supports all the newer versions of Windows including Windows
7, Vista, XP, and 200x which are not compatible with tthe Cisco DialOut
NetDialOut can create up to 256 virtual communication (COM) ports under
Windows. Each of these virtual COM ports can be redirected to a modem
server located anywhere on a network (or over the internet)..
Modem Pooling is a function of the modem server which allows allows
each client to automatically connect to the next available modem assigned
to a pool (group) of modems on the modem server, rather then connecting
to a specific modem every time. Cisco Access Servers refer to modem
pools as rotarys in the Cisco IOS.
Here is how it works:
- You configure your modem server to allow Dialout access on one or
- You configure the NetDialOut to to redirect at least one Windows
virtual COM port to the modem server.
- When a client application opens a virtual COM port, it gets redirected
to a modem on the modem server.
- Easy to Install and use.
- Supports all popular versions of Windows, including Windows 7, Vista
and Server 2008.
- Automated Server Failover, if primary server is full or unavailable.
- Dynamic routing table creation.
- Security by user authentication: Windows Credentials or Login/Password.
- Powerful client diagnostics allows application debugging.
- Compatible with MS Dial-Up Networking, Fax (Class 2 & 2.0),
and most other communication applications for Windows or DOS.
- Uses the TCP/IP Telnet protocol, with the RFC-2217 Telnet extentions
for COM Port Control.
- NetDialOut virtual COM ports run as a high performance kernel-mode
2. Software Installation Quick Guide
This Quick Guide is intended for users familiar with installing Windows
based software. The information below will enable you to get your NetDialOut
redirector up and running, as quickly as possible.
We still recommend you read the entire guide to become familiar with
Operating System Software:
- Windows 7, Vista, XP, 2008, 2003, 2000, or NT 4.0-SP6 - all
32-bit and 64-bit (x64) versions.
All editions are supported: Professional, Home, Workstation, Server,
Premium, and Ultimate.
- NetDialOut also supports Windows Small Business Server, Hyper-V,
Windows Terminal Server and Citrix XenApp/XenApp
environments are also supported in the Site Edition of NetDialOut.
- PC equipped with an Intel Pentium compatible processor, single
or multi core.\
- Network Card (configured to use the TCP/IP Protocol).
- At least the minimum RAM recommended by Microsoft to run your
version of Windows.
- At least 5 megabytes of free hard drive space.
- A Network Access Server (NAS), or a similar Modem Server or device
server such as a router or gateway with serial ports or modems attached,
which supports the RFC-2217 protocol extentions. A Cisco Access Server
or Router requires IOS version 12.0.(9) or higher.
Software Installation and Configuration Overview:
Here is a list of the steps needed to install the Client Software, which
are explained in chapters 5, 6 and 7:
- Log onto Windows with an account that has Administrator access.
- Install the NetDialOut Redirector software.
- In the Select Ports window, choose which virtual
COM port(s) you wish to create and click OK.
Usually only one virtual COM port is needed.
- In the NetDialOut Configuration Window, enter
the IP address or hostname of the Modem Server.
- Enter the TCP/IP port which the Modem Server accepts incoming connections
on. For a Cisco NAS we suggest using TCP/IP port 7000..
- If the Modem Server is a Cisco NAS is configured to use Authentication,
Authorization, and Accounting (AAA), then set NetDialOut to use
Security (either a login/password, or Windows authentication).
- Click the Test Server Connection to confirm that
thet virtual COM port can access the Modem Server.
- Repeat steps 4,5,6 and 7 for each additional new COM port you created.
- Click the "Save" button, and the "Install
Modem Driver" window will automatically appear.
- Click Add Modem Driver to run the Add
Hardware Wizard to install the proper modem driver on the
virtual COM port(s).
- Set your application software to use one of the NeDialOut virtual
COM ports, or the name of the modem driver attached to one of the
NetDialOut virtual COM ports.
3. Installing the NetDialOut Software
The NetModem Client software should be installed on each PC in which
you want to access the modems (or other serial devices) whose COM ports
are defined in the NetModem Server shared ports list. The Client PC's
can be running any version of Windows 7, Vista, XP, 2008, 2003, 2000,
or NT 4.0-SP6. The client can also be installed under Windows Terminal
Services, Remote Desktop, Citrix XenApp, VMware, or Virtual PC. A Client
PC can be running any Intel Pentium compatible processor, and should
have at least the minimum amount of RAM suggested by Microsoft to run
the version of Windows installed.
Before installing the NetDialOut Redirector Software:
- Make sure you are logged into Windows as a user with Administrator
- If you are performing an upgrade, exit any programs that are using
virtual COM ports.
- Determine if you will use the 32-bit (x86) version of the
NetDialOut installer, or the the 64-bit (x64) version. If you
are installing it on a 32-bit version of Windows, you must use the
32-bit (x86) installer. If you are installing it on a 64-bit version
of Windows, you must use the 64-bit (x64) installer.
Run the NetDialOut installer to begin the Installation Wizard.
It will take you though the following steps:
- Review the License Agreement and indicate whether you accept
the terms or not. If you do not accept the terms, the software will
not be installed.
- Select the Destination Folder to install to. The default
is c:\program files\NetDialOut\
- Review or change any settings, and Begin Installation. It
should only take a moment to install.
The installation should only take a moment to finish. Once it completes,
you will automatically be taken to the NetDialOut "Select Ports"
window shown below.
4. Configuring the NetDialOut Software
NetDialOut can create from 1 to as many as 256 virtual COM ports,
which are each redirected by NetDialOut to access shared COM ports located
on the modem server. The first step is to select which virtual COM port(s)
you wish have NetDialOut create.
COM ports can be numbered from COM1 up to COM256. Most desktop
PC's come with one or two physical COM ports, usually named COM1
You will only be able to select COM ports that don't already exist
on the Windows PC. In the image to the right COM1 and COM2 are
not show in the list because they already exist on this PC's motherboard.
Most applictions only require one COM port, in which case you
only need to select one virtual COM port, even if you have several
modems installed on the modem server. The virtual COM port numbers
do not need to match the COM port values on the Access Server.
Some older communication applications only allow selecting a COM
port between COM1 and COM4, inclusive. Therefore its usually best
to select a virtual COM port numbered below COM5.
You can always change to a different virtual COM port, or add/remove
virtual COM ports at a later time. This can be done by right clicking
the NetDialOut tray icon, and selecting "Configure"
to get to the NetDialOut Configuration window, and choose "Select
Under special applications including Terminal Services you may
want to create several virtual COM ports. You can select or unselect
a range of ports by clicking the first COM port, then hold down
the Shift key as you click on the last COM port in the
range, then click on either the Select Highlighted or Unselect
Once you have selected at least one virtual COM port and clicked OK,
the NetDialOut Configuration Window should appear. You can manually
get to this by right-clicking on the NetDialOut system tray icon
in the lower right on your taskbar (by your clock), and selecting "Configure".
The NetDialOut system tray icon looks like this:
The NetDialOut Configuration window allows you define the Server IP
address and TCP Port for each virtual COM port, and optionally which
remote COM port it should redirected to.
The Server IP Address should be set to the IP address
of the NAS or Modem Server.
The TCP Port should be the value defined in your NAS or
modem server. For Cisco Access Servers configured for Modem Pooling,
use port 7000).
Security should only be enabled if your NAS or modem server
reqests a username and password when a client connects to it.
The Use Multiple Server Failover checkbox allows a list of Failover
servers to be configured. NetDialOutt can automatically go to other
servers if the primary server is either full or unreachable.
See the Using
Multiple Servers for Failover chapter for details.
The Security options are:
None , Use Login/Password , Use Windows Credentials ,, and Prompt at
The default Security is None, which does not attempt to send a login
or password to the Modem Server.
If the NetModem Server's Pool Properties requires the client to provide
authentication, then NetDialout should be configured appropriately.
See the Security Settings chapter
The Encryption options are:
None , TLSv1 or SSLv3 , TLSv1 only , and SSLv3 only.
The default Encryption is None, which uses no encryption between the
client and server. See the SSL/TLS
Encryption chapter for details.
The command buttons on the NetModem Client Configuration window are
Select Ports - Choose which Virtual COM ports should be created
for NetModem Client.
Test Server Connection - Tests the connection to the Modem Server.
Save - Saves changes without closing the Configuration window.
Close - Closes the NetModem Client Configuration window, and
Advanced - Allows configuring advanced options. See the Client advanced
options chapter for details.
Help - Displays the user's guide.
Once you have assigned the correct Server IP address, TCP Port, and
redirect method to each of the virtual COM ports, you should verify
that each virtual COM port can communicate with the NetModem Server
by selecting the COM port, and then clicking the Test Server Connection
The Security options are: None, Use Login/Password and Use Windows
The default is None, which does not attempt to send a login or password
to the Modem Server.
If the Access Servers IOS system is set for AAA, then NetDialOut should
be configured for either "Use Login/Password" or "Use
Windows Credentials". For more information see the Security
The command buttons on the NetDialOut Configuration window are as follows:
Select Ports - Choose which Virtual COM ports should be created
Advanced - Select the close port delay, and choose to see a pop-up
message if a port is not available.
Test Server Connection - Tests the connection to the Modem Server.
Close - Closes the NetDialOut Configuration window, and saves
Once you have assigned the correct Server IP address and TCP Port to
each of the virtual COM ports, you should verify that each virtual COM
port can communicate with the NAS or Modem Server by selecting the COM
port, and clicking the Test Server Connection Button.
The Server Connection Test:
This test allows you to verify that the client can communicate
with the server, and can fix any detected setting errors.
The top settings are filled with the current COM port settings.
If connecting to non-modem devices on the NetModem Server,
then disable the checkbox to check for the presence of
Click the "Start" button to begin the test. If
everything is successful the results will look like the image
on the right.
After the connection is made to the server, it confirms that
the server is using both the Telnet Protocol and the RFC-2217
Telnet Protocol extension. If both of these are not detected,
you probably connected to something other then a NetModem Server.
If you have enabled the checkbox to check for the presence of
a Modem then the test will finish by sending an "AT"
command to the modem, and confirms that the modem responds with
If each of the created virtual COM ports tested with similar results
as above, then you have successfuly configured NetDialOut.
When the test stops, you can click on "Start" to test
the port again, or click "Use Settings" to accept any
changes that were made to your settings. The "Copy Log"
button allows you to copy the test results to the clipboard, allowing
it to be pasted into a document or email. The "Cancel"
button exits the test without saving.
Once you have successfully configured the virtual COM ports which were
created, and you Save or Close the NetDialOut Configuration
window, you will be provided with a reminder to install modem drivers
which will guide you through the process outlined below.
5. Installing the Modem Driver
The NetDialOut virtual COM ports by default do not have any modem devices
(drivers) attached to them.
Most Windows DialOut Applications require a modem driver to be present
in order to dial out, but some applications do not require a modem driver
as they communicate directly with the Windows COM port. We suggest installing
a modem driver for compatibility with the widest range of applications.
A modem driver is a text file with an .INF extention, and may
or may not include additional driver files.
By installing a modem driver on each virtual COM port, you create that
number of modem devices on the PC.
It is usually nessesary to install the correct modem driver on the virtual
COM port(s), because a mismatched
driver can often lead to compatibility issues.
If your Modem Server is a Cisco Access Server or Cisco Router with modems
attached,, then you will need one of the modem drivers listed below,
which are available for download from the Cisco ftp site.
||AS5350,AS5400 AS5800, AS5850
||Microcom DeskPorte V.34 FAST
||mdmrock5.inf (or the standard 28800 bps modem file)
For other brands of modem servers, refer to the manufacturer of your
hardware. Many modem servers are able to use the Windows Standard 56k
or 33.6k modem drivers built into Windows, but it is always the best
practice to use the actual modem driver provided by the manufacturer
if one is available..
To open the "Phone and Modems" control panel manually,
Go to the Windows Control Panel (click Start > Control
Panel) and locate the "Phone and Modems" icon.
You may need to switch to "Classic View" to locate
this. Double click on the icon to enter the "Phone and Modem
Options" Window. Then click on the "Modems"
tab at the top, and it will show you which modems are currently installed.
Click the "Add" button at the bottom to add a modem
Enable the "Don't detect my modems, I will select it from a
list" checkbox, and then click "Next".
Click the "Have Disk" button. DO NOT Click "Next".
Enter the path to your modem drivers .INF file, either by typing
it and click OK, or Browse for it.
A list of one or more modem models will be displayed. If there is more
then one choice, be sure to select the one being used on the Modem Server..
A list of available COM ports is displayed. Click the "Selected
ports" option, and click the virtual COM port which you selected
in the NetDialOut Configuration window (In this case it is COM4). Click
Your modem driver should now be installed. Click "Finish".
You should now see the modem driver is "Attached To"
the Client Virtual COM port. If no COM port is listed here, then something
went wrong with the modem driver installation.
If your modem driver can not be installed on the virtual COM port for
any reason, please contact a technical
support engineer for assistance.
Assuming the modem driver installed successfully, your installation
is now complete. All that is left is to configure your application software
to use the new COM port (or to use the Modem Driver attached to that
6. Monitoring Activity on the Virtual COM ports
You can display the NetDialOut Monitor Status screen by right clicking
the NetDialOut system tray icon
and selecting Status.
Each Virtual COM port created by NetDialOut is Listed under "Ports"
in the Status screen.
When a COM port is open, its Baud, State, and IP Address
fields will appear.
After a COM port is closed, these fields are removed a few seconds later.
Baud: The number of times per second that an RS-232 serial signal
can change on this port.
values are 300,1200,2400,9600,19200,38400,56700, and 115200.
State: The number of Data Bits, Parity Type, and number of Stop
Bits the port is configured for.
the above "8,N,1" means 8 Data Bits, No
Parity, and 1 Stop Bit.)
IP Address: The IP Address of the Modem Server (NAS) which this
COM port is redirecting to.
The following buttons are usually available are on the right:
Configure: Opens the NetDialOut Configuration Window. (This
button may be removed by the Administrator to prevent users from making
changes to the configuration).
Help: Opens the Users Guide.
About: Displays the copyright and contact information.
Client users can monitor the Data Flow occurring on all of the Virtual
COM ports by selecting the Trace Tab in the NetDialOut Monitor.
The trace Window normally only displays messages when virtual COM ports
are created or removed, or the virtual serial port driver is restarted.
When you select the Enable Trace checkbox, you are shown the
serial data moving to and from the client and server along with the
timestamp and name of the COM port. You can also enabled the Hex
Display checkbox to show the data in hexadecimal numeric format
instead of the default ASCII code format, and you can enable Auto
Scroll checkbox to have the window scroll as more data is logged.
There are three color codes used in the trace data:
- Control Information
Black text preceded with a "|" is Control Information, such
as a changing Status Line, Baud Rate, or State setting, or when a
COM port is opened or closed.
Blue text preceded with a "»"is
data transmitted over the COM port by the application software.
This can be viewed in either ASCII code format, or Hexidecimal numeric
Red text preceded with a "«"
is data received over the COM port by the application software.
This can be viewed in either ASCII code format, or Hexadecimal numeric
There are three buttons used to control the log:
Clear: Erases the entire log from the window.
Save Log: Saves the log file in either ascii format (.log) or
binary format (.trc)
Open Log: Opens a binary format (.trc) trace file that was previously
Enabling the Trace can be a valuable tool for troubleshooting misconfigured
Trace should normally be left disabled, as enabling it causes a slight
decrease in the performance and also increases the amount of RAM used.
7. Security Settings
Some Cisco Access Servers have an IOS option called AAA, which
stands for Authentication, Authorization, and Accounting. Enabling AAA
on a Cisco Access Server causes it to request a users login/password
credentials when a client PC connects to a modem on the Access Server,
which it then authenticates via a RADIUS authentication server.
Many other modem servers support some form of user authentication.
NetModem Server can be used
to authenticate from a Windows PC using Active Directory or a
local domain , and this can be used as a front end to NetDialOut . Doing
this also provides the benifit of an SSL/TLS encripted connection between
the clients and NetModem Server..
If your modem server is configured to use authentication, then NetDialOut
must be configured with a security setting to pass either the Windows
Credentials of the current user, or a Login/Password to the modem server.
You can enable the security options in NetDialOut by right clicking
the NetDialOut Tray icon
and select Configure.
The NetDialOut Configuration Window allows you setting different
security settings for each Virtual COM port you have defined.
The following Security options are available
Use Windows Credentials
The default is None, which does not try to send any security
information when it connects to the modem server.
Use Login/Password will provide the server with a login and
password each time a virtual COM port is opened. When you select this
security option, a button will appear that says "Change Login/Password".
allows you to define the Login name of the user, and their password.
The Login Name and password provided must match an account found
on the modem server or on the authentication server that the modem
server is configured to use.
The Password prompt requires you enter a password twice, to confirm
that you typed it correctly.
Use Windows Credentials will provide the server with the current
user's Windows login information each time a virtual COM port is opened.
NetDialOut obtains this information from Windows during the login process.
After the NetDialOut is installed, the user will need to logoff and
then login again before this option will be functional.
Once you have enabled one of the security options in the NetDialOut
Configuration, you should run the "Test Server Connection"
to make sure that the security handshaking between the client and server
8. SSL/TLS Encryption
8. 1 Encryption overview
The SSL/TLS Encryption feature allows the data passed between the NetDialOut
virtual COM port and the modem server to remain secure, even when used
an insecure network such as the internet. NetDialOut requires a special
license key in order to enable encryption, and the modem server must
also support SSL/TLS encryption and must be configured with compatible
Either the SSL version 3, or TLS version 1 cryptography protocols can
be used. TLS is more advanced then SSL, and is therefore recommended.
Both protocols support several different encryption algorithms (which
are known as Ciphers), and each cipher supports several key lengths
(which are known as Encryption Strengths).
NetDialOut supports the following ciphers: RC2, RC4*, DES, 3DES, and
Multiple encryption strengths are available for each cipher, which
ranges from 56 bits to 256 bits depending on the cipher.
When Encryption is enabled, Each NetDialOut Client PC can request an
SSL Certificate from the modem server, and can use this to validate
the servers identity by confirming that the certificate was issued and
signed by a Certificate Authority (known as a CA). A built-in list of
CA's (exported from Internet Explorer 6), is included with NetDialOut,
or a custom list of CA's can be used instead. NetDialOut also allows
unsigned/self-signed certificates to be used.
8.2 Enabling Encryption
For encryption to be used, both NetDialOut and the Modem Server must
both be configured to enable configuration and to negotiate a common
protocol, cipher, and cipher strength.
- Open the NetDialOut Configuration window, and on the Encryption
pull-down menu select one of the following::
TLSv1 or SSLv3
It is best to select the "TSLv1 or SSLv3" option,
as this allows the Server to choose which will be used.
- Click the Advanced button, and from the Advanced window click
on the SSL Encryption tab.
- Select the Minimum / Maximum Encryption Strengths
and the Encryption Ciphers that NetDialOut will offer to negotiate
with the Server. You will need to have at least one Cipher selected
which the modem server has also been configured to allow.
- To assure that the Certificate supplied by the modem server has
the correct credentials, you should enable the Require Validated
Common Name checkbox. By default there will be a %C in the Common
Name Field, which is a meta-tag used in place of the Servers Hostname
or IP Address, as defined in each COM port configuration screen. This
should always be used when you have more then one Server the client
will connect to.
Optionally, you could enable the Require Validated Organization
checkbox, which will allow you to specify the name of the organization
the Certificate was issued to.
When either of these checkboxes are enabled, the Client will require
the servers demand that the Servers certificate
When either of these checkboxes are enabled, the client will demand
that the field(s) defined them are an exact match for the same fields
defined in the Servers certificate. You can leave these fields blank
to be filled in automatically when you test the server connection
in step 7 below.
- If the modem server is using a sample certificate or some other
unsigned certificate then you should select the Do not require
a certificate to be signed option.
If you are using a certificate signed by a known CA (Certificate Authority)
then you should select the
Use built-in Certificate authority file option.
If the modem server is using a certificate signed by a CA not listed
in the included CA.PEM textfile, then you can either select Do
not require a certificate to be signed or Provide a custom certificate
authority file. Review the CA.pem file to for information on creating
a custom CA file.
- Click the OK button to close the Advanced window.
- In the NetDialOut Configuration window, click the Test Server
Connection button to verify that the Encryption options you specified
are compatible with the settings defined on modem server.
- If there are any encryption issues found by the test, it will ask
you if you wish to fix the problems. Answering yes will change the
encryption options on the client to match what the server requires.
If this is done, be sure to review the Advanced SSL Encryption settings
afterwards to see what settings have been changed.
- Once the test is successful, be sure to click the "Use Settings"
button at the bottom of the test window.
You can see which Encryption Cipher is being used by each active COM
port in the NetDialOut Monitor Status Window.
Note: Changes made to the NetDialOut Configuration change effects subsequent
sessions. Current sessions are not effected.
9. Using Multiple Servers for Failover
If you have multiple modem servers are used, you can allow NetDialOut
to maintain a list of servers to attempt to connect to each time a Virtual
COM port is opened. If the first server on the list is either full or
unreachable for any reason, NetDialOut tries the next server on the
The NetDialOut Configuration Screen looks different when Use
Multiple Server failover enabled. The usual input fields for
IP Address and TCP Port, are replaced with the Server List options.
These allow you to choose from several different lists of modem
servers, and will allow you to edit any one of those lists.
Up to 20 Server Lists can be defined, and each server list allows
up to 5 Servers to be specified.
In the Edit Server List you can defined up to 5 servers
to be specified, in the order you want NetDialOut to connect to.
A Server list needs at least two servers defined. Each Server
entry must have the IP Address (or hostname) of the Server, and
the TCP Port. A Pool Name is optional, if no Pool Name is defined,
the default pool will be accessed.
When an application opens a COM port that is configured to use
multiple servers, NetDialOut first attempts to connect to the
first server on the list. If that server is either full or unreachable,
the client attempts to connect to the next server on the list.
This continues until a server with an available modem is reached,
or until all the servers have failed.
When using multiple servers, you can fine tune how long NetDialOut
waits for each server to respond when the Client requests a COM port
from a server. By default it waits up to 3 seconds for the server to
respond, and if there is no response then it switches to the next server
in the list. The settings can be found under the "Advanced"
button in the NetDialOut Configuration window. The value is in milliseconds
(1/1000th of a second), so the default value of 3000 = 3 seconds maximum.
On a slow Network you might need to increase this value, and on a Network
in which Several Failover Servers are defined, you might need to decrease
the value in order to speed up the search.
10. Troubleshooting and Technical Notes
If the "Test Server Connection" Fails.
First check that the NetDialOut COM port has the correct IP address
of the modem server defined, and the correct TCP port which has been
configured for modem pooling on the NAS or modem server.
If that does not solve it:
Find out if the modem server is accepting connections by going to a
Command Prompt, and running TELNET.EXE by typing in the following
and press [Enter] :
telnet 192.168.0.1 7001 (replace 192.168.0.1 with
the IPaddress of the modem server, and replace 7001 with the
TCP port of the modem server.
A black empty screen indicates a successful connection.
A "Could not open connection to the host" response
indicates that the Access Server is not accepting incoming connections
on that TCP port.
A "Login:" prompt indicates a sucessful connection,
which requires Security to be enabled in NetDialOut.
11.2. Solving Network Faxing Issues.
Only Class 2 or Class 2.0 fax modems can be
used over a network, due to Class 1 being very timing sensitive.
Most NAS and advanced modem servers support Class 1, Class 2, and Class
2.0. faxing. It's a good idea to check which fax class is supported
with the modem servermodem manufacturer before purchasing a NAS or other
The Faxing software you use also needs to be configured for Class 2
or Class 2.0. Keep in mind that Class 2 and Class 2.0 are not the same,
so it's important that the software is configured for a fax class that
is supported by modem(s) located on the NAS or modem server.
Consult your faxing software documentation for information on setting
Class 2 or 2.0 in your faxing software.
There is also some information on this subject found on PC Micro's NetDialOut
11.3. Using NetDialOut under Terminal Services or Citrix XenApp.
Windows Terminal Services, Remote Desktop and Citrix XenApp are multi-user
environments which can be used with the Site Edition of NetDialOut.
Terminal Services is part of Windows Server server (2008,2003,2000,NT4)
which enable users to access Windows-based programs are installed on
a terminal server, or to access the full Windows desktop. With Terminal
Services, users can access a terminal server from within a corporate
network or from the Internet.
Remote Desktop is a light single-user version of a terminal server included
in Windows Professional, Business, and Ultimate Versions. Citrix XenApp
is an advanced remote access infrastructure server for enterprise applications.
When using any of these environments to allow "Thin-Clients"
to access the shared COM ports, you should use the following procedure:
- Install NetDialOut Site Edition on the Terminal Services Server,
Remote Desktop, or XenApp PC.
- Select one virtual COM port in the NeDialOut configuration, and
assign the IP address of the modem server.
- Next Select as many additional Virtual COM ports as needed. (Usually
you will want to select one virtual COM port for each thin-client
user). Up to 256 Virtual COM port can be selected. All the additional
virtual COM ports will default to using the same Server IP address
as you assigned in step 2.
- When you close the client configuration window, you will be guided
to install a modem driver. When you are instructed to select the ports
to assign the modem driver to, select all the Virtual COM ports.
- Assign one of the Virtual COM ports to each thin-client user. This
will allow each user to access the next Shared COM port on the server
though their virtual COM port. This allows up to 256 thin-clients
to access the modem pool.
- If the modem server is configured to require User Authentication,
the NetDialOut Security setting may not be set for "Use Windows
Credentials". Instead the "Use Login/Password"
security setting must be used. This is because Terminal Services and
Citrix XenApp will not allow NetDialOut to access the current users
To configure Windows 7, Vista or XP (non-home version) to become a
Remote Desktop, you should use the following procedure:
- Right-click My Computer, click Properties, and then
click Remote tab.
- Turn on Remote Desktop by selecting the check box Allow users
to remotely connect to this computer.
- Designate users by clicking the Select Remote Users button.
Remapping COM ports in Windows Server 2008 or Server
Windows Server 2008 and Server 2003 (all versions except the Web Edition)
includes a command line utility called change.exe which can map
any COM port to a different port number under the current users Terminal
For example, a Terminal Services user could enter this command:
change port COM12=COM1
This allows the current user to access COM1 in their application software,
which is redirected to COM12 by Windows Server. COM12 could be either
a physical COM port, or a virtual COM port created by NetDialOut.
A second Terminal Services user could enter this command:
change port COM13=COM1
Now both users can access COM1 at the same time in their application
software, and they will really be using COM12 and COM13 respectively.
This allows all users to use application software configured for a particular
COM port, and allows legacy applications that only supported COM1-COM4
(or in some cases COM1-COM9) to be used by more then 4 or 9 Terminal
Services users at the same time. However, this will not work with TAPI,
so applications that need to communicate with a Modem Driver name rather
then a COM port value can not take advantage of this feature.
The change port command can be used as part of each users login
script to map COM1 to a specific NetDialOut virtual COM port which is
reserved for that user. For example if COM99 is reserved for a particular
user, the following would be added to that users login script: change
You can run change port without any parameters to display the available
COM ports and the current COM port mappings.
A limitation of the change port command is that the new COM
port exists only in memory, and is not written to the registry HKEY_LOCAL_MACHINE\HARDWARE\DEVICEMAP\SERIALCOMM
which is where many application programs look to see which COM ports
exist. One solution would be to create a dummy registry entry in this
registry folder like this:
In which FAKE could be any unique name, and COM4 could be any unique
COMx value. Making changes to the registry should only be done by an IT
professional familiar with the precautions involved in registry editing
such as backing up the registry first.
Limitations under Terminal Services, Remote Desktop,
and Citrix XenApp
- Only one outbound PPP (Point to Point Protocol) connection can be
made at a time from any Windows PC, even under a multi-user operating
system such as Terminal Services Server, Remote Desktop, and Citrix
XenApp. This is not a limitation of NetDialOut, but rather a limitation
For example, A Dial-Up Networking connection to an ISP uses the PPP
protocol. This causes the Windows routing table to be changed so that
all TCP packets that are sent outside of the local subnet are directed
to this PPP connection. If another PPP connection is created, Windows
again changes the routing table which causes the first PPP connection
to fail. If you need to allow multiple users to be able to make simultaneous
PPP connections, you will need to install NetDialOut on each users
- Citrix XenApp prevents more then one outbound VPN (Virtual Private
Networking) Connection to be made using a modem.
- If a VPN connection is used to connect to the network containing
NetDialOut, then it is not possible to make a secondary VPN connection
through NetDialOut. This is due to a limitation in the VPN protocol.
Additional Information on Terminal Services and Remote Desktop can be
found at Microsoft's web site using the following links:
Remote Desktop Frequently Asked Questions:
How to deploy Terminal Services under Windows Server 2008:
How to deploy Terminal Server under Windows Server 2003:
Windows Server Terminal Services Home Page:
11.4. Preventing accidental client configuration changes.
If the Administrator is concerned about the possibility of a client
user misconfiguring the virtual com port settings, then the configure.exe
file can be removed from the NetModem Client folder. This is usually
located in c:\program files\netmodem\client\
11.5. NetDialOut advanced configuration options
To access the NetDialOut advanced configuration options, click on the
Advanced button from the NetModem Client Configuration screen.
The following options are found under the Options tab:
- Delay closing COM port for  ms.
When this option is enabled, it causes NetDialOut to remain connected
to the server (and the physical modem) for the specified amount of
time in milliseconds that begins when the virtual COM port is closed
by the application. This ensures that the modem is not assigned to
another user while an application closes and reopens the virtual COM
port, and ensures that an active connection is not lost if one application
or process hands off a COM port to another one.
By default this option is Enabled, with a value of 7500 ms. (7.5 seconds).
- Update Routing Table if needed
When this option is enabled, NetDialOut will add a direct route
to the modem server when a virtual COM port is opened, if the modem
server is not on the same subnet as the NetDialOut PC and there is
not already a direct route defined. Once the virtual COM port is closed,
the added route will then be removed. The reason for adding a direct
route, is that some PPP applications such as Windows Dial-Up Networking
will change the computer's default route in the IP routing table when
they have established a connection to the remote network. Once this
change is made, the NetDialOut PC will no longer have a route to the
modem server if the two PC's are not on the same subnet. Without a
valid route, the NetDialOut PC will lose its connection to the modem
Some third-party VPN software will not permit changes to the routing
table. If the NetDialOut PC is connected to the modem server through
a VPN, this option may need to be disabled. In such a case, the VPN
users would be unable to use NetDialOut to establish a dial-up networking
By default this option is Enabled.
- Maximum time to wait for a Failover Server
When this option is enabled, and the NetDialOut virtual COM port
is configured to use Multiple
Server Failover this option will limit the time that NetDialOut
waits for each server to respond before it gives up and attempts to
connect to the next server in the failover list.
By default this option is Enabled, with a value of 3000 milliseconds
- Synchronize with server during COM port open
When this option is enabled, each time an application requests
to open a virtual COM port, the
COM port open request is not completed until the following events
occur between the client and server:
1. The TCP connection to the server is established.
2. The SSL/TLS encryption negotiation is established (if encryption
3. The COM Port Control protocol is negotiated.
4. The user authentication is sucessful (if security is used).
Some applications may require that the COM port open function will
synchronize with the server by waiting until the server provides the
modem before returning a sucess status, or returning a fail status
By default this option is Disabled, allowing the virtual COM port
to be opened immediately.
11.6 NetDialOut Virtual COM port driver
NetDialOut uses a highly optimized kernel-mode driver to create its
virtual COM ports.
The virtual COM port driver can be found in the device manager under
"Non-Plug and Play" drivers (you will need to enable
"View > Hidden devices" to see it).
The driver is controlled by a service in Windows. NetDialOut virtual
COM ports can be reconfigured by third party applications, by writing
to the VCOMM registry folder located here: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\VCOMM
11.7 Support for DOS Applications
NetDialOut is compatible with both Windows applications and many DOS
applications running under Windows. Generally a DOS application which
uses a COM port will do so by accessing the serial port hardware directly.
This hardware is called a UART, which stands for Universal
32-bit versions of Windows 7, Vista, XP, 2000, and NT include a subsystem
to run DOS applications known as the NTVDM, an acronym for NT
Virtual DOS Machine. The NTVDM monitors the standard
UART I/O ports for activity by DOS applications on COM1, COM2, COM3,
and COM4. The NTVDM redirects any activity on these ports to the Windows
COM port of the same name. For this reason, DOS applications can only
be used with NetDialOut on virtual COM ports COM1-COM4.
Some DOS applications allow you to configure the UART settings for the
COM ports. The NTVDM only works with the standard UART settings shown
While most DOS applications communicate with a COM port directly through
the UART, there are a few DOS applications that can communicate by using
the PC's BIOS Interrupt 14h or an enhanced version of the Interrupt
14h interface called a FOSSIL driver. If your DOS application
says that it is compatible with Interrupt 14h or a FOSSIL, then you
can install a third-party FOSSIL driver such as ADF or NetFoss, which
can enhance performance of your DOS communication software. ADF is a
free program which can be downloaded from https://digsys.se/adf.html
An example command line to load ADF on COM4 would be:
ADF.exe COM4 2E8 3 57600 4096 1024
This should be loaded in the same DOS window that your DOS application
is started from afterwards, which can be easily done in a batch file.
For more information on ADF, please refer to the ADF documentation.
ADF is a DOS driver, so it will only work on COM1-COM4.
NetFoss is a free FOSSIL driver designed to use Windows COM ports, so
it will allow FOSSIL compatible DOS applications to work on any COM
port value. You can download NetFoss from https://pcmicro.com/netfoss
12. Request Technical Support
Our technical staff has many years of experience in solving communication
related issues, and provide real guidance even on tough problems that
take trace log analysis or network packet analysis to figure out.
You can request support online at https://pcmicro.com/netdialout/support.html
or contact your PC Micro account manager for assistance. You can also
email email@example.com. Initial response time is usually under
an hour or two between 7:00AM - 7:00PM PST (Pacific Standard Time
GMT-7 ) Weekdays, and limited hours during weekends and US Holidays.
If you purchased or are evaluating NetDialOut through a local reseller
or a consultant, they may provide an additional level of technical support.
13. Update the License Key
NetDialOut has two licensing methods availabe:
- The Standard version is licensed per Seat,
meaning that each PC running NetDialOut needs a seperate license key.
- The Site Edition version is licensed by the maximum
number of simultanious connections that can be made by all
the users at your site. The NetDialOut Site Edition software can be
installed on an unlimited number of PCs at the site, and the total
number of connections is monitored by the included License Manager
software. The Site Edition does not require a license key for each
PC, as only the License Manager requires a key.
The Standard version of NetDialOut allows a fully functional 30 day
evaluation if no license key is entered into NetDialOut. If you decide
to purchase a license key, you are provided with an electronic license
certificate (PDF file) which contains a license key that can be entered
into the NetDialOut to unlock the 30 day limitation.
To update your NetDialOut Standard version License Key, do the following:
- Open the NetDialOut Monitor window by double clicking on the system
- Select the License button. The current license information
is displayed, including how many days are left if the software is
running in evaluation mode.
- Select the Change button.
- Type in your License Key in the field titled License Key.
- Optionally type in the User Name and Company Name.
- Select OK to accept the new information.
The Site Edition version does not require a licence key in NetDialOut
, instead it it requires the IP address of the PC running the License
Manager. To select enter the IP address of the License Manager, do the
- Open the NetDialOut Monitor window by double clicking on the system
- Select the License button. The current IP address of the
License Manager PC is displayed.
- Enter the new IP address of the License Manager PC
- Select OK to accept the new information.
14. Uninstalling the NetDialOut Software
To Uninstall the NetDialOut software do the following:
- Navigate to the Windows Control Panel and select the "Add
or Remove Programs" Icon
- Select NetDialOut in the list of installed programs.
- Click the Change/Remove button to begin the Uninstall process.
- Select Uninstall, and click Next.
- After uninstalling NetDialOut,, remember to also remove any modem
drivers that were attached to the virtual COM ports. This can be done
from the "Phone and Modem Options" in the Windows Control
Windows does not need to be restarted after installing or uninstalling
the NetDialOut softwarere.
Copyright © 1997-2009 PC Micro
Systems and Odin Software. Portions Copyright © 1997-2009 Microsoft
Corporation. Portions Copyright © 1998-2009 The OpenSSL Project.
This product includes software developed by the OpenSSL Project for
use in the OpenSSL Toolkit (https://www.openssl.org). All Rights Reserved.
NetDialOut and PC Micro are Trademarks or Registered Trademark of PC
Micro Systems, Inc. Windows and Microsoft are Trademarks or Registered
Trademarks of Microsoft Corporation. WinFax and pcAnywhere are Trademarks
or Registered Trademarks of Symantec. Citrix, XenApp and XenApp are
Trademarks or Registered Trademarks of Citrix Systems, Inc. RC2 and
RC4 are Trademarks of RSA Security, Inc. VMWare is a Trademark or Registered
Trademark of VMware, Inc. Cisco and IOS are registered trademarks of
Cisco Systems, Inc.