Nowadays most Linux distributions run a firewall by default and it results in blocking of the TCP/UDP ports required to be used for Xmanager. Because the firewall programs used in Linux are various through out all distributions and versions, you might need to refer to user manuals or technical support service for your the Linux distribution you use. The following instruction is for ipchains and iptables, which are the most common firewall tools for Linux.

To run a remote X program, your IP address should be a public one that can be reached from the remote host because a remote program tries to connect to your local PC.

If your PC is located inside the firewall or NAT and the Unix host is located outside, X applications cannot connect to the Xmanager running on your PC.

There are two solutions on this situation:

• By using SSH connection
• By configuring port forwarding rules on the NAT system

SSH connection

In case of using SSH connection, you do not have to configure other options. It establishes a secure tunnel between PC and Unix, so we recommend that you use SSH protocol if the Unix server supports it.

Secure XDMCP is a new feature that will change how people access their remote hosts. Learn how to obtain CDE or GNOME/KDE environment under the NAT environment using Secure XDMCP.


To start an X application through SSH protocol, please go through the following steps:

1. Run Xstart in the Xmanager folder.
   
2. Select SSH for Protocol.
   
3. Enter username, password, hostname, etc.
   
4. Fill the Execution Commnad box as following:
   /usr/bin/X11/xterm -ls

   *Note that -display option is absent. SSH server will assign a proper value.
5. Click Save and Run button.
   
6. The Xstart will automatically run Xmanager and then execute the remote command.
   
7. In the command prompt of xterm window, execute startkde for KDE, gnome-session for Gnome or Xsession for CDE.
   * Please refer to the following link to find out more commands for starting each UNIX/Linux desktop environment:
   
   
     FAQ Link

   • How can I start CDE or GNOME/KDE environment using Xstart?

Port forwarding rules on the NAT System

To use port forwarding, you should forward the port 6000 of NAT system to the port 6000 of your PC. In case of multiple local users, you can do the following steps: (NAT, 6001) -> (PC1, 6000)
(NAT, 6002) -> (PC2, 6000)
. . .
(NAT, 6009) -> (PC9, 6000) To make XDMCP connection, you need to setup proxy options in the session properties. (*The following instruction is for the PC1.)

1. Create a new XDMCP session in Xbrowser.
2. Open the session properties and select 'Use following connection address' in the Proxy area of the General tab.
3. In the Host text box, type the IP addreass of the NAT server.
4. In the Port Number text box, type the port number you have assigned in the NAT system for your PC. (6001 for the PC1)
5. Clear 'Allocate display number automatically' in the Display Number area of the X Server tab.
6. Type the remaining number when subtracting 6000 from the port number in the step 4 above. (1 for the PC1)

For connections using Xstart, each user has to enter "-display" option as following: PC1: /usr/bin/X11/xterm -ls -display $NATsystem:1
PC2: /usr/bin/X11/xterm -ls -display $NATsystem:2
. . .
PC9: /usr/bin/X11/xterm -ls -display $NATsystem:9

If I'm inside a firewall using IP Masquerading, how can I connect to external Linux/Unix hosts? (ex. kernel 2.2) Run the following command as a root on your firewall server. # ipmasqadm portfw -a -P tcp -L FIREWALL_ADDRESS 6001 -R PC_ADDRESS 6000 Run Xstart program and enter the following command at Command field. /usr/bin/X11/xterm -ls -display FIREWALL_ADDRESS:1.0 Be sure that, firewall_address and PC_address have been changed to the corresponding IP addresses on your own network. If you do not have ipmasqadm tool, please download from the following site: http://www.e-infomax.com/ipmasq/juanjox/

You should open the following TCP/UDP ports.

• From remote host to local PC (Inbound):
  - TCP 6000 ~ 6010 for Xmanager
  - *TCP 16001 for Gnome only
• From local PC to remote host (Outbound):
  - UDP 177 for XDMCP
  - TCP 512, 513, 514, 23, 22 for Xstart

*Note: Gnome may fail to login or logout if TCP 16001 port is not allowed.

If Xmanager session is left idle, the connection may get disconnected. In the router or firewall between your PC and UNIX/Linux server, you may have the 'Connection Timeout' option enabled. This option disconnects network connections if no data is transferred for a specified time period. Please make sure to set this option to your desired time length.

Windows XP/2003 may block all incoming TCP/IP connections. So, Xmanager cannot be used without allowing its listening port. Please do the following steps to enable Xmanager connection:

1. Open Control Panel, Network and Internet Connection, and then Network Connections.
2. Right-click on your Internet connection, and then click Properties.
3. Click Settings. RESULT: Advanced Settings dialog box will open.
4. Allow TCP 6000 ~ 6010 and *TCP 16001 port.
   * For Gnome only

If Windows XP Service Pack 2 is installed on your machine, follow the procedure below:

1. Open Control Panel, and then Windows Firewall.
2. From the General tab, select On (recommended) option.
3. Click the Exception tab.
4. Click the Add Program button.
5. From the Programs list, select Xmanager - Passive.
6. Click OK.