LRS Reference Manual

10 - Modem Sharing

10.1 - Introduction

10.2 - Services

10.2.1 - Creating a Service
10.2.2 - Associating Ports with a Service
10.2.3 - Displaying Current Services

10.3 - IPX

10.3.1 - IPX Service Configuration

10.3.2 - Redirector

10.3.2.1 - Redirector Requirements
10.3.2.2 - Installation
10.3.2.3 - Configuration
10.3.2.4 - Using the Redirector

10.4 - IP

10.4.1 - Connecting to a TCP Listener Service
10.4.2 - Connecting to an LRS Serial Port
10.4.3 - Connecting to an LRS Service or Port

10.5 - Examples

10.5.1 - Configuring the LRS
10.5.2 - Configuring the Redirector
10.5.3 - Configuring the PC Communications Software

10.6 - Troubleshooting

10.6.1 - General
10.6.2 - IPX

10.7 - Quick Reference

10.1 Introduction

Modem sharing provides users with individual modem/phone line functionality at a reduced cost. When modems are shared, a group of IP or IPX users may use a modem pool to dial out of a LAN and connect to a remote host; for example, to connect to a bulletin board service (BBS). This eliminates the need for phone lines for each user's computer.

10.2 Services

A service represents a resource accessible to network users; for example, a modem or a pool of modems attached to the LRS.

Services provide links for TCP or SPX (Sequenced Packet Exchange) connections to LRS serial ports. They are employed in modem sharing to establish connections to the LRS modems.

10.2.1 Creating a Service

Each LRS service must have a unique name. To create a service, use the Set/Define Service command. An example is displayed below.

Figure 10-1: Creating a New Service

Local>> DEFINE SERVICE fastmodems
Service names are not case-sensitive, may be up to 16 alphanumeric characters long, and cannot include spaces.

10.2.2 Associating Ports with a Service

Each service must be associated with at least one port. To associate a port with a service, use the Set/Define Service Ports command:

Figure 10-2: Associating a Port with a Service

Local>> DEFINE SERVICE fastmodems PORTS 2
To use a service for modem sharing, the service should be associated with multiple ports; this permits multiple connections to the service. Connections will be made to the first available port.

Figure 10-3: Associating Service With Multiple Ports

Local>> DEFINE SERVICE fastmodems PORTS 2-4
Ports associated with a service used for modem sharing must support outgoing connections. To support outgoing connections, the port access must be set to Dynamic or Remote.

Figure 10-4: Configuring a Port for Outgoing Connections

Local>> DEFINE PORT 2 ACCESS DYNAMIC
A port associated with a service used for modem sharing must also be configured to operate the modem attached to it. To configure modem operation on a port, use the following commands:

Figure 10-5: Configuring Modem Operation on a Port

Local>> DEFINE PORT 2 MODEM CONTROL ENABLED
Local>> LIST MODEM
Local>> DEFINE PORT 2 MODEM TYPE 5
To display a particular modem type's settings, use the Show/List Modem <type #> command.

For more information on modem configuration, see Chapter 9 - Modems. For more information on port configuration, see Chapter 8 - Ports.

10.2.3 Displaying Current Services

To display a list of the current services, use the Show/Monitor/List Services command.

To display specific information about a service, the following parameters may be used with the Show/Monitor/List Services command: Characteristics, Summary, and Status. For example, to display a service's characteristics (including the ports associated with it), use the following command:

Figure 10-6: Displaying a Service's Characteristics

Local> LIST SERVICES fastmodems CHARACTERISTICS

10.3 IPX

10.3.1 IPX Service Configuration

For services on an IPX network, the LRS uses the SPX protocol to manage the connection to a remote host. To enable SPX on a service, use the Set/Define Service SPX command:

Figure 10-7: Enabling SPX on a Service

Local>> DEFINE SERVICE fastmodems SPX ENABLED

10.3.2 Redirector

The Lantronix IPX Redirector is an application that allows PCs that are on an IPX network to share modems connected to the LRS when using Microsoft Windows communication applications. Using the Redirector, PC users can use their communication software to dial out, connect to a modem available as an LRS service, and connect to a remote host.

The Redirector intercepts communications to specified COM ports and sends them over an SPX connection to an LRS serial port. This enables the PC to use the LRS serial port as if it were one of the PC's COM ports.

To determine the available services, the Redirector checks the NetWare bindery. The bindery receives information about the available services from SAP packets and continually updates its list of services. The LRS will issue SAP packets when SPX is enabled; to enable SPX, see IPX Service Configuration .

The Redirector permits only one logical port to be active at a time. The communications software cannot establish simultaneous connections using multiple redirected ports.

10.3.2.1 Redirector Requirements

The Redirector requires the following:

DOS 3.0 or higher, Windows 3.1, or Windows for Workgroups 3.11
Windows communications software
A NetWare 3.x or 4.x server with bindery emulation

10.3.2.2 Installation

The Redirector is shipped on the LRS CD-ROM. For installation instructions, see the Redirector Installation Notes on the CD-ROM.

The Redirector must be installed on each PC that will share LRS modems.

10.3.2.3 Configuration

A Windows setup utility is provided to configure the Redirector. To run the utility, double-click the Lantronix IPX Redirector Setup icon.

When the Redirector is launched, the Setup Summary window will appear.

Figure 10-8: Setup Summary Window

The Port Assignments area displays information about the redirection of each COM port.

The status area displays the current status of the Redirector. This area will display one of the following messages:

Table 10-1: Redirector Status Messages

Message Explanation
Idle The Redirector is loaded and is successfully communicating with the setup utility, but is currently idle.
Redirecting COM <number> to The Redirector has an open SPX connection to a service. The name of the service and the COM port number should be displayed.
Connection failed A network error caused the connection to fail.
Connection terminated by server The LRS closed the connection. This may be caused by a privileged user logging out the port.
To redirect a COM port, click the Change button to the right of the port. The Service Selection Window will appear.

Message	Explanation
Idle	The Redirector is loaded and is successfully communicating with the setup utility, but is currently idle.
Redirecting COM <number> to	The Redirector has an open SPX connection to a service. The name of the service and the COM port number should be displayed.
Connection failed	A network error caused the connection to fail.
Connection terminated by server	The LRS closed the connection. This may be caused by a privileged user logging out the port.

Figure 10-9: Service Selection Window

All available LRS services are displayed in the Known Services area. The list will be obtained from the NetWare bindery each time the Redirector setup utility is executed. If new services are added to the bindery while the setup utility is running, they will not be displayed in the Known Services list until the next time that the setup utility is run.

To configure this COM port to redirect data to a service, double-click the service name. Up to four services may be associated with each COM port.

As services are associated with the COM port, they will be displayed in the Selected Services area. When configuration is complete, the Redirector will redirect data to the first available service in this area.

To change the order of the services in the list, select a service name and click the First and Last buttons. To remove a service from the list, click the Remove button.

When you've finished configuring the COM port, click the OK button. The Setup Summary window [Figure 10-8 ] will appear. To complete the redirection, click the check box to the left of the COM port number.

When you've finished configuring all ports, click the Done button.

10.3.2.4 Using the Redirector

Once installed, the Redirector will load itself whenever a redirected port is accessed. It will display a dialog box when it connects to or disconnects from a service.

Figure 10-10: Redirector Loading

10.4 IP

To share LRS modems, IP users must do one of the following:

Form a TCP connection to a TCP listener socket associated with a service
Form a TCP connection directly to an LRS serial port
Log into the LRS and connect to a local service or port

These methods are discussed in the following sections.

10.4.1 Connecting to a TCP Listener Service

Each service may be associated with a TCP listener socket. TCP connections to the socket are connected to the service. Once a connection is established, a user may issue commands to the modem.

To associate a service with a TCP listener socket, use the Set/Define Service TCPport command. Socket numbers must be between 4000 and 4999.

Figure 10-11: Specifying a Raw TCP Listener Socket

Local>> DEFINE SERVICE highspeedmodem TCPPORT 4999
If the socket should perform Telnet IAC character-escaping negotiations on the data stream, use the Set/Define Service Telnetport command:

Figure 10-12: Specifying a Telnet TCP Listener Socket

Local>> DEFINE SERVICE highspeedmodem TELNETPORT 4500
Connecting to a TCP listener service is recommended if more than one modem is being used. The LRS will automatically connect the user to the next available modem; the trial and error process of finding an available port (see Connecting to an LRS Serial Port ) will be avoided.

10.4.2 Connecting to an LRS Serial Port

To connect directly to an LRS serial port, specify a port number of 3000 + n, or 2000 + n. The n represents the number of the LRS serial port; for example, port 2002 represents LRS serial port 2.

If you're using Telnet to connect to the LRS, connect to port 2000 + n. The 2000 port is intended for Telnet connections; it performs Telnet IAC character-escaping negotiations on the data stream. In the example below, the Telnet command is used to connect to LRS serial port 3.

Figure 10-13: Telnetting Directly to Port 3

% TELNET server_name 2003
If you're connecting via a host application, connect to port 3000 + n. This port provides an 8-bit clean connection, required by most host applications.

10.4.3 Connecting to an LRS Service or Port

To connect to a local service or port from an LRS login, use the Connect Local command at the Local> prompt.

Figure 10-14: Connecting to a Local Service/Port

Local>> CONNECT LOCAL fastmodems
Local>> CONNECT LOCAL PORT_2
If a service name is specified, a connection is made to the first available port associated with the service. If a port name is specified, the connection is made to the port unless the port is in use.

Once the connection is established, commands may be issued to the modem attached to the serial port.

10.5 Examples

Users on an IPX network must connect to a BBS and a commercial online service. The following modems are available:

Two 28,800 bps modems, reserved for connections to the online service
Four 14,400 bps modems, available for connections to both services
One 9,600 bps modem, reserved for connections to the BBS

10.5.1 Configuring the LRS

The modems are connected to an LRS16 as follows:

Table 10-2: Modems Connected to the LRS

Modems Connected to LRS Modem Type #
Two 28,800 bps modems Ports 2 and 3 6
Four 14,400 bps modems Ports 4 -7 5
One 9,600 bps modem Port 8 4
To display the list of LRS modem types (profiles), use the List Modem command.

Modems	Connected to	LRS Modem Type #
Two 28,800 bps modems	Ports 2 and 3	6
Four 14,400 bps modems	Ports 4 -7	5
One 9,600 bps modem	Port 8	4

Three services will be created for the modems: fastmodems, slowmodems, and slowestmodem. These will be used for the 28,800, 14,400, and 9,600 modems, respectively.

The LRS must be configured as shown below:

Figure 10-15: LRS Configuration

Local>> DEFINE SERVICE fastmodems PORTS 2-3 SPX ENABLED
Local>>
Local>> DEFINE PORT 2-3 ACCESS REMOTE
Local>> DEFINE PORT 2-3 MODEM TYPE 6
Local>> DEFINE PORT 2-3 MODEM CONTROL ENABLED
Local>>
Local>> DEFINE SERVICE slowmodems PORTS 4-7 SPX ENABLED
Local>>
Local>> DEFINE PORT 4-7 ACCESS REMOTE
Local>> DEFINE PORT 4-7 MODEM TYPE 5
Local>> DEFINE PORT 4-7 MODEM CONTROL ENABLED
Local>>
Local>> DEFINE SERVICE slowestmodem PORT 8 SPX ENABLED
Local>>
Local>> DEFINE PORT 8 ACCESS REMOTE
Local>> DEFINE PORT 8 MODEM TYPE 4
Local>> DEFINE PORT 8 MODEM CONTROL ENABLED
Local>>
Local>> LOGOUT PORT 2-8
Local>> INITIALIZE DELAY 0

10.5.2 Configuring the Redirector

The following table shows how the Redirector setup utility should be configured for this example. All three LRS services should appear in the Service Selection window.

The Service Selection window is shown in Figure 10-9 .

Table 10-3: Redirector Configuration

COM Port # Redirect? Selected Services
(in order)
COM Port 1 Yes fastmodems
slowmodems
COM Port 2 Yes slowmodems
slowestmodem
COM Port 3 No None
COM Port 4 No None

COM Port #	Redirect?	Selected Services (in order)
COM Port 1	Yes	fastmodems slowmodems
COM Port 2	Yes	slowmodems slowestmodem
COM Port 3	No	None
COM Port 4	No	None

10.5.3 Configuring the PC Communications Software

The communication software must be configured as follows:

Connects to the online service by dialing out through COM Port 1
Connects to the BBS by dialing out through COM Port 2

10.6 Troubleshooting

The following sections list some common problems associated with modem sharing and proposes solutions for them.

10.6.1 General

If commands issued to a modem aren't displayed, the modem may not be configured to echo commands. To correct this problem, enable modem echoing on the modem.

If a connection attempt fails, check the port's access. The access must be set to dynamic or remote in order to support outgoing connections. Failed connections may also result if the port is currently in use.

10.6.2 IPX

Table 10-4: IPX Troubleshooting

Problem Possible Cause(s) Remedy
The Redirector setup utility can't see any services. There is a problem with the NetWare bindery. For NetWare 4.x, enable bindery emulation.
The LRS is not advertising its services. If IPX routing is enabled, use the Show/Monitor/List IPX command to ensure that the correct frame type and network number are enabled. In addition, ensure that SAP Send is enabled.

The Redirector can't connect to an LRS service. A port can't initialize its attached modem. Logout the port. Check the modem initialization string.
The COM port is not configured to redirect serial data to one or more LRS services. Configure the COM port to redirect data to its list of Selected Services.
All ports associated with the service are busy. Use the Show/Monitor/List Services Characteristics command and examine the Rating field. If the service rating is 0, all ports associated with the service are in use.

10.7 Quick Reference

Using Services For Modem Sharing: Step by Step Configuration
To	Use This Command	Example(s)	What Example Does
Create a Service	Set/Define Service	DEFINE SERVICE fastmodems	Creates a new service named "fastmodems". See Creating a Service for more information.
Associate Ports with a Service	Set/Define Service Ports	DEFINE SERVICE fastmodems PORTS 2-4	Associates the "fastmodems" service with ports 2, 3, and 4. See Associating Ports with a Service for more information.
Configure a Port to Support Outgoing Connections	Set/Define Port Access Remote/Dynamic	DEFINE PORT 2 ACCESS REMOTE	See Access to a Port for more information.
Configure a Port to Support Modem Operation	1. Define Port Modem Control Enabled	DEFINE PORT 2 MODEM CONTROL ENABLED	Enables modem operation on port 2.
	2. Define Port Modem Type	DEFINE PORT 2 MODEM TYPE 5	Associates port 2 with modem profile 5. The port will be configured in accordance with the modem profile. See Modem Profiles for more information.
Display Existing Services	Show/Monitor/List Services	LIST SERVICES fastmodems CHARACTERISTICS	Displays the characteristics of "fastmodems", including any associated ports. See Displaying Current Services for more information.
IPX
To	Use This Command	Example(s)	What Example Does
Enable SPX on a Service	Set/Define Service SPX Enabled	DEFINE SERVICE fastmodems SPX ENABLED	Enables SPX on the "fastmodems" service. See IPX Service Configuration for more information.
Configure and Use the Redirector	See Redirector.
IP
To	Use This Command	Example(s)	What Example Does
Create a TCP Listener Socket	1. Set/Define Service TCPport	DEFINE SERVICE highspeedmodem TCPPORT 4999	Associates the "highspeedmodem" service with TCP listener socket 4999. TCP connections to 4999 will be connected to "highspeedmodem". See Connecting to a TCP Listener Service for more information.
	2. Set/Define Service Telnetport	DEFINE SERVICE highspeedmodem TELNETPORT 4500	Associates the "highspeedmodem" service with TCP listener socket 4500. TCP connections to 4500 will be connected to "highspeedmodem", and Telnet IAC character-escaping will be performed.
IP, cont.
To	Use This Command	Example(s)	What Example Does
Connect Directly to an LRS Serial Port	Connect Telnet 2000 + <serial port #>or	TELNET server_name 2003	Connects user to LRS serial port 3; Telnet IAC character-escaping will be performed. See Connecting to an LRS Serial Port for more information.
	Connect Telnet 3000 + <serial port #>	TELNET server_name 3003	Connects user to LRS serial port 3; this is an 8-bit clean connection.
Connect to a Local Service or Port From an LRS Login	Connect Local	CONNECT LOCAL fastmodems	Connects to the local "fastmodems" service. See Connecting to an LRS Service or Port for more information.
		CONNECT LOCAL port_2	Connects directly to LRS port 2.

LRS Reference Manual - 4 MARCH 1996

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Problem	Possible Cause(s)	Remedy
The Redirector setup utility can't see any services.	There is a problem with the NetWare bindery.	For NetWare 4.x, enable bindery emulation.
	The LRS is not advertising its services.	If IPX routing is enabled, use the Show/Monitor/List IPX command to ensure that the correct frame type and network number are enabled. In addition, ensure that SAP Send is enabled.

The Redirector can't connect to an LRS service.	A port can't initialize its attached modem.	Logout the port. Check the modem initialization string.
	The COM port is not configured to redirect serial data to one or more LRS services.	Configure the COM port to redirect data to its list of Selected Services.
	All ports associated with the service are busy.	Use the Show/Monitor/List Services Characteristics command and examine the Rating field. If the service rating is 0, all ports associated with the service are in use.