I think my serial port(on board) is not working ......
because when I am running same code on two machines its working good....but when my system comes into picture ....it doesnt show any output comming from serial port..........

can anybody tell me how to configure my serial port.........or to check it is installed on ot or not...........

moreover I had inserted another card having two serial ports.....
info about card:::::::::::::::::::is here
05:04.0 Serial controller: Timedia Technology Co Ltd PCI2S550 (Dual 16550 UART) (rev 01) (prog-if 02 [16550])
Subsystem: Timedia Technology Co Ltd Unknown device 4037
Flags: stepping, medium devsel, IRQ 10
I/O ports at 1100 [size=32]

but how to configure/install ....this card.
I am using fedora core 6
thanks & regards.........

1. If the operating system says the device exists, eg if that does not return an error, the serial port is configured for the OS.

2. The next part is RS232 debugging, here always start with a known working terminal and go through the different combinations with a null-modem and even a break-out-box.

but whem I am running command ::::
dmesg | grep tty
It shows:::::::
[root@arun ~]# dmesg | grep tty
Xen virtual console successfully installed as ttyS0
.....
what does it means...my onboard serial is configured or not?????
and if configured then why I am not able to send or recieve data....

also when I am using command::

[root@arun ~]# setserial -g /dev/ttyS0
Cannot get serial info: Invalid argument

why so??????????
i thing so that its not configured correctly............

Are you running as a virtual host, not a real machine?

Can I modift it or not??????
So how to make it real console????????
please help........

You don't want it as a real console, you want it connected to a serial port.

So the reasons things don't work when "when my system comes into picture" is because you don't have a real machine, everything is virtually provided by Xen. This may make writing software easier but it makes tracking comms problems down much harder because you now have to try and get the Xen environment to provide you with the real serial port.