Using VNC to access serially connect computers

 

The SDT features in all Opengear console servers enables remote users to use VNC (or any other appropriate in-band network connection protocol) to connect to computers and other intelligent devices that are network connected or serially connected to the console server. VNC will give the user remote access to all of the applications, files, and network resources, with full graphical interface just as though they were in front of the computer screen. 

The instructions below detail setting up a VNC-SDT Connector via serial/PPP link through an Opengear console server.The computer that is the end point (running the VNC Server software) will hereafter be referred to as the server. The system that is running the VNC Viewer software and the SDT Connector software will be hereafter referred to as the client.The following steps also are shown using Red Hat for both the server and client operating systems: 

A pre-requisite on the server is to have the VNC Server software setup and tested before attempting to set up the link over serial PPP. 

On the server the following files need to be created or edited: 

#/etc/ppp/options
lock
noauth
#/etc/ppp/pap-secrets
# Secrets for authentication using PAP
# client server secret IP addresses
* * "" 10.233.111.254

Options specific to the serial line you are connecting with are placed in /etc/ppp/options.ttySn, where n is the number of the serial device.

#/etc/ppp/options.ttyS0
asyncmap 0
crtscts
#local indicates that modem lines are not used 
local
connect 'chat -v -f /etc/ppp/scripts/cm4xxxclient.chat'
require-pap
115200
lcp-echo-failure 1
lcp-echo-interval 5
#/etc/ppp/scripts/cm4xxxclient.chat
TIMEOUT 3600
CLIENT CLIENTSERVER\c

You can have the PPP daemon (pppd) start when you boot the system and have it monitor the serial line of your choice. An elegant way of achieving this is to edit the /etc/inittab file. This file contains information for initializing the system. Add the following to the end of this file:

#/etc/inittab
# Start pppd for the serial laplink.
pd:2345:respawn:/usr/sbin/pppd /dev/ttyS0 nodetach

The nodetach option makes that pppd stays connected to the terminal that started it, rather than forking and exiting. This option is necessary because the "init" process would respawn a new one immediately otherwise. To activate this new configuration type:

#/sbin/init q

You should be able to check the /var/log/messages on the server to see if pppd has been started, and see that chat has started and is now waiting to receive the CLIENT string.

#/var/log/messages
Jun 6 09:47:04 localhost pppd[8142]: pppd 2.4.3 started by root, uid 0
Jun 6 09:47:04 localhost chat[8146]: timeout set to 3600 seconds
Jun 6 09:47:04 localhost chat[8146]: expect (CLIENT)

If you made it this far, congratulations your server is now setup. 

Now you have to setup the console server to connect to the server to allow SDT connections. On the Management Console's Serial & Network menu choose Serial Port. Next edit the serial port that you desire to use. Set the Common Settings for the port to 115200 Baud rate, 8, None and 1 with Flow control set to None. 

Then select SDT mode leaving the Username and User Password fields blank. 

 

Now if the serial cabling has been setup between the console server and the server they should be connecting to each other. You can check the /var/log/messages on the server and it should show something similar to:

#/var/log/messages
Jun 6 09:47:04 localhost pppd[8142]: pppd 2.4.3 started by root, uid 0
Jun 6 09:47:04 localhost chat[8146]: timeout set to 3600 seconds
Jun 6 09:47:04 localhost chat[8146]: expect (CLIENT)
Jun 6 09:47:40 localhost chat[8146]: CLIENT
Jun 6 09:47:40 localhost chat[8146]: -- got it
Jun 6 09:47:40 localhost chat[8146]: send (CLIENTSERVER)
Jun 6 09:47:40 localhost pppd[8142]: Serial connection established.
Jun 6 09:47:40 localhost pppd[8142]: Using interface ppp0
Jun 6 09:47:40 localhost pppd[8142]: Connect: ppp0 <--> /dev/ttyS0
Jun 6 09:47:41 localhost pppd[8142]: local IP address 10.233.111.1
Jun 6 09:47:41 localhost pppd[8142]: remote IP address 10.233.111.254

If your /var/log/messages looks similar to this then you have a successful serial PPP connection between the server and the CM4xxx.

All that is left to do is setup the SDT Connector software on the client to utilize the serial PPP link to forward your VNC session.

In your SDT connector software on the client you need to specify the gateway IP address of your CM4xxx and a username/password for a user you have setup on the CM4000 that has access to the desired port.

Next you need to add a New SDT Host. In the Host address you need to put portxx where xx = the port you are connecting to. Example for port 1 you would have a Host Address of: port01 Select the VNC Service check box. 

 

Now you can click on the VNC button and it will launch the VNC viewer and ask for the VNC password. 

 

Now your VNC connection is running over the serial PPP link.