Moxa Tech Note

Reverse Telnet Mode for NPort

Reverse Telnet Mode for NPort
Moxa Technical Support Teamsupport@moxa.com
This Tech Note applies to NPort 5000, NPort 6000, and NPort Wireless Plus device
servers. The following models are included:zzzzzzNPort 5100 series
NPort 5200 series
NPort 5400 series
NPort IA5150 and IA5250
NPort W2150 Plus and W2250 Plus
NPort 6000 series

What is Reverse Telnet Mode?
In Reverse Telnet Mode, the Telnet session is initiated from the network. The
serial device waits for the network host to initiate the connection. Typically,
Reverse Telnet Mode is used for console server applications, where a network hostTelnets to a device's console port for configuration or maintenance. TCP Server
Mode is similar in that it involves a serial device acting as a server. However, TCP
Server Mode does not convert CR/LF characters.
Ethernet

PC running telnet
program

RS-232NPort

Copyright © 2008 Moxa Inc.

SW/Router/Server s
console port

Released on July 15, 2008

About Moxa
Moxa manufactures one of the world’s leading brands of device networking solutions. Products include serialboards, USB-to-serial hubs, media converters, device servers, embedded computers, Ethernet I/O servers,terminal servers, Modbus gateways, industrial switches, and Ethernet-to-fiber converters. Our products are key
components of many networking applications, including industrial automation, manufacturing, POS, and medical
treatment facilities.

How to Contact Moxa
Tel:1-714-528-6777
Fax: 1-714-528-6778

Web: www.moxa.com
Email: info@moxa.com

This document was produced by the Moxa Technical Writing Center (TWC). Please send your comments orsuggestions about this or other Moxa documents to twc@moxa.com.

Moxa Tech NoteReverse Telnet Mode for NPort

Configuring the NPort for Reverse Telnet Mode
Before performing the following steps, restore the NPort device server's default
settings by holding the reset button down for 10 seconds.
Also, please note that for NPort Wireless Plus models, only one network interface(WLAN or Ethernet) can be active at a time. To use the Ethernet interface, makesure the network cable is plugged in before powering on the NPort. To use theWLAN interface, make sure the network cable is unplugged when the NPort is
powered on.
1.

Turn the NPort on. The Ready LED should turn green.

2.

Make sure that the NPort and the host PC are properly connected to thenetwork.

3.

Adjust the NPort's IP settings as necessary so that it is in the same network
as your PC. You may also need to modify the host PC's IP configuration.
Make sure you can ping the NPort from your host PC.
Remember, the IP addresses of the NPort and the PC must be on the same
subnet. If one IP address is modified, you may need to modify the other IPaddress.

4.

On the host PC, connect to the NPort's Telnet console by entering telnet<NPort's IP address> at the command prompt. For example, if your NPort's
IP address is 192.168.127.254, enter telnet 192.168.127.254 at thecommand prompt.

5.

In the Telnet console under Port > Modes, set Application to Reverse
Terminal and Mode to RTELNET. Under Description/more settings, set
Map keys <CR-LF> to as necessary for the device's console.

6.

In the Telnet console under Port > Line, adjust the communication
parameters as necessary for your terminal, such as 115200, N, 8, 1.

7.

In the Telnet console, select Save/Restart to restart the NPort with thenew settings activated.

Testing Reverse Telnet Mode for the NPort
Ethernet

PC running telnet
program

RS-232

NPort

SW/Router/Server sconsole port1.

Set the NPort's serial port to Reverse Telnet Mode as described above and toRS-232.

2.

Use an RS-232 null modem cable to connect the device's console port to theNPort's serial port.

3.

At the command prompt, enter telnet <NPort's IP address> 4001 (e.g.,telnet 192.168.254.127 4001). The command prompt can be opened in

Copyright © 2008 Moxa Inc.

Page 2 of 3

Moxa Tech NoteReverse Telnet Mode for NPort

Windows through Start Æ Run… and entering cmd.
4.

You should enter the device's console and be able to see messages normally.
If messages are not displayed normally, you may need to adjust the<CR-LF> mappings on the NPort.

Cable Wiring

Copyright © 2008 Moxa Inc.

Page 3 of 3