Hung Port


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Operating Systems HP-UX Hung Port
# 1  
Hung Port

Here's a difficult one for you.

I am on HPUX 11.0. I have a hung port, it is stuck in FIN_WAIT_2. Short of rebooting, how can I terminate the connection the system thinks still exists? I found a script online that uses adb but have not been able to get it to work. I am still open to using adb but have not been able to figure it out on my own, mostly becuase my background is Sun and HPUX is slightly different.Smilie Smilie
# 2  
The usual reason for asking this question is that you want to restart a server but can't because you get a message "can't bind to port". There are adb scripts to close a FIN_WAIT_2 socket, I don't understand why you're having trouble with it. HP also has a program called ndd which can close a connection. But you shouldn't have to do this. Instead you address the real problem which is that the server has a bug that should be fixed.

There are two ways to ignore FIN_WAIT_2 sockets under unix. First, a program like inetd can do the bind at boot-up time and pass off new connections to the server as they arrive. Second, the server can simply set the SO_REUSEADDR option to indicate that it would prefer to ignore them.

You must have a server that does not want to run under inetd and it doesn't set SO_REUSEADDR. Ask whoever wrote the server to fix that. It takes one line of code to set SO_REUSEADDR and then you will have no more problem.
# 3  
Thanks for the insight. I will see if I can get the program changed, which I am sure will take some time. In the mean time I will keep working the the adb script and check out ndd. If anyone has tips on adb troubleshooting, let me know.
# 4  
I think ndd is for tuning only. You can use it to change timeout thresholds and things like that, but you can't use it to clear a port that has been left open to my knowledge. Anyone know how if this IS possible?
# 5  
Wha't up Doeboy, Long time no see Smilie

I think you are right. I thought there might be tuning parm to set the TTL on the connection, but all settings I could see are global so this would not help me. I think adb is the only way out. Guess I will keep searching for a working script and keep trying to tweak the one I have (which was created on HPUX 8 by the way, I have tried to update it for 11 but must be missing something in the adb command).
# 6  
Remember that we are talking HP-UX here. HP's man page for ndd mentions "ndd -h unsupported". If you run:
ndd -h unsupported | grep disco
you will see:

tcp_discon - Terminate a TCP connection
tcp_discon_by_addr - Terminate a TCP connection

I have never had a TCP connection that I want to terminate, so I have never tried them. But I know several people who claim that they do work. Why are you saying that ndd can't do this? Did you guys try these and find that they don't work?
# 7  
Hung Port

Hi,

I used the below script to clear the FIN_WAIT socket connections. ( HP unix )

for i in $(ndd -get /dev/tcp tcp_status | grep xxx.xxx.xxx.xxx | grep TCP_FIN_WAIT | awk '{print $1}' )
do
ndd -set /dev/tcp tcp_discon 0x${i}
if [ $? -eq 0 ]
then
echo "Cleared $i"
else
echo "Unable to clear $i"
fi
done


xxx.xxx.xxx.xxx = the destination server IP.
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