Xmanager FAQ

XDMCP Connection Show all answers Hide all answers

Session declined. Maximum number of open sessions from your host reached

Systems utilizing gdm (or gdm-binary) through an XDMCP daemon may see a message which states that the session was declined because the maximum number of open sessions from your host was reached.

gdm limits the number of XDMCP sessions which can connect from a single IP address. Some Linux distributions limit the number to 2 connections. In this case, you will not be able to open more than 2 XDMCP sessions to the same Linux machine from the same PC.

If you attempt more than 2 sessions, the XDCMP daemon will block the connection and you will see an error message stating the maximum number of open sessions from your host was reached.

To change the limits of the number of connections allowed, please use the following instructions:

1. Edit the /etc/gdm/custom.conf or gdm.conf file.

[xdmcp]

Enable=true

DisplaysPerHost=10 (<=enter the desired limit)


2. Restart the top-level process within the gdm(or gdm-binary) processes.

#ps -aef |grep dm |grep -v grep

root     20483     1  0 16:01 ?        00:00:00 /usr/sbin/gdm-binary -nodaemon

root     24855 20483  0 23:04 ?        00:00:00 /usr/sbin/gdm-binary -nodaemon


# kill -1 20483

Session declined. Maximum number of open sessions reached

Systems utilizing gdm (or gdm-binary) through an XDMCP daemon may see a message which states that the session was declined because the maximum number of open sessions was reached.

This means that gdm is currently putting a limit on the number of XDMCP sessions. The default limit is set to 16 connections and as such the total number of XDMCP sessions that are able to connect to the machine is 16.

To change the default limit, please use the following instructions:

1. Edit the /etc/gdm/custom.conf or gdm.conf file.

[xdmcp]

...

MaxSessions=99 (<= gdm does not support over 99 XDMCP sessions.)


2. Restart the top-level process within the gdm(or gdm-binary) processes.

#ps -aef grep dm grep -v grep

root     20483     1  0 16:01 ?        00:00:00 /usr/sbin/gdm-binary -nodaemon

root     24855 20483  0 23:04 ?        00:00:00 /usr/sbin/gdm-binary -nodaemon


# kill -1 20483


When I connect to UNIX by XDMCP, the CDE session hangs.

1.   I cannot see the login window.
If you cannot see the login window, you need additional fonts for the host. You can download and install the fonts in your Unix server or you can set up a font server.
To run font server in host:
  1. Run xfs.
  2. Run fsinfo -server host_IP_address:7100.
To configure Xmanager:
  1. Start Xconfig in Xmanager2 folder.
  2. Open the properties of the profile for the session.
  3. Select Font tab.
  4. Add Font Server.
  5. Save the changes and run Xmanager.
Also, one of the following reasons might prevent CDE connection from being made:
  • The Unix server is not located in the same subnet as your PC.
  • Your PC has multiple IP addresses.
  • Name server has an invalid name-to-ip or ip-to-name entry for your PC. Check the forward and reverse lookup tables.
  • See the /var/dt/Xerrors file for more detailed information.
2.   The CDE login window shows up. After login, the session hangs or is terminated.
The $HOME/.dtprofile might have a line that prevents a successful login. You need to try to comment all commands out in the file. Also, remove the following lines in your login scripts:
export DISPLAY=:0.0
or
setenv DISPLAY :0.0
For more detailed reasons, please see $HOME/.dt/errorlog.

I entered the correct username and password in the login screen but it is only showing the black screen.

When the DISPLAY variable is manually assigned, the remote machine may not find X server (Xmanager). DISPLAY variable is set automatically by Xmanager so you do not need to manually assign it.
Please check your login script (.cshrc, .profile, .login, .bashrc, and etc) and comment out the line that starts with "export DISPLAY..." or "setenv DISPLAY..." as the following statements.
# export DISPLAY=192.168.1.xxx
# setenv DISPLAY 192.168.1.xxx

XDMCP connection fails for Linux. How do I configure my Linux box?

How to configure Linux XDMCP(KDE/GNOME) settings for Xmanager:
Affected Files
For runlevel :   /etc/inittab
For GDM : /etc/X11/gdm/gdm.conf
/etc/gdm/custom.conf (Fedora Core 5)
For KDM : /etc/X11/xdm/xdm-config
/etc/X11/xdm/Xaccess
/etc/X11/xdm/kdmrc
/usr/share/kdm/kdmrc
/usr/share/config/kdm/kdmrc
/etc/opt/kde2/share/config/kdm/kdmrc
For Firewall : /etc/sysconfig/ipchains
Step 1. Change runlevel to enable gdm or kdm.
  1. Open /etc/inittab file.
  2. Change the runlevel to 5 as following:
    id:5:initdefault:
Step 2. GDM configuration (When the Linux is using gdm)
  1. Open /etc/X11/gdm/gdm.conf file. (/etc/gdm/custom.conf for Fedora Core 5)
  2. Go to the [xdmcp] section.
  3. Set the value of Enable option to true or 1.
Step 3. KDM configuration (When the Linux is using kdm)
  1. Open /etc/X11/xdm/xdm-config file.
  2. Comment out "requestPort" option as following:
    DisplayManager.requestPort: 0
    ==>
    !DisplayManager.requestPort: 0
  3. Open /etc/X11/xdm/Xaccess file.
  4. Remove the initial "#" character for the following line:
    #* #any host can get a login window
    ==>
    * #any host can get a login window
  5. Open /etc/X11/xdm/kdmrc,
    /usr/share/config/kdm/kdmrc or
    /etc/opt/kde2/share/config/kdm/kdmrc file.
  6. Change the value of "Enable" option to "true".
Step 4. Firewall configuration (If the firewall has been configured)
  1. Open /etc/sysconfig/ipchains file.
  2. Add the following lines at the top of the file:
    -A input -p udp -s 0/0 -d 0/0 177 -j ACCEPT
    -A input -p tcp -s 0/0 -d 0/0 telnet -j ACCEPT
    -A input -p tcp -s 0/0 -d 0/0 ssh -j ACCEPT
    -A input -p tcp -s 0/0 -d 0/0 login -j ACCEPT
    -A input -p tcp -s 0/0 -d 0/0 exec -j ACCEPT
    -A input -p tcp -s 0/0 -d 0/0 shell -j ACCEPT
    -A input -p tcp -s 0/0 -d 0/0 7100 -j ACCEPT
Step 5. Restart your Linux to activate the changes.

When I use GDM, I cannot make a Secure XDMCP connection.

In some GDM versions, you may have problem making Secure XDMCP connections because the connection address cannot be translated correctly. To use Secure XDMCP, change display manager to 'kdm' or 'xdm'. The following instructions show how to switch your display manager to 'kdm' or 'xdm'.

Note: You are not changing the desktop environment such as Gnome or KDE. This process will simply change the login in screen.
  1. Stop the gdm process using gdm-stop or init 3 command
  2. Start display manager with kdm or xdm command

I am trying to connect to SUN Solaris/HP-UNIX/IBM AIX using XDMCP, but I get the error message: "XDMCP Connection failed."

In order to use XDMCP connection, CDE login should be enabled on your remote server.
Follow the instructions below to enable CDE login :
  1. Login as a root.
  2. Enable CDE login when system boot:
    $ /usr/dt/bin/dtconfig -e [enter]
  3. Reset the process: dtconfig -reset
If you want to disable the CDE login setting, do the following :
$ /usr/dt/bin/dtconfig -d [enter]