Socket connection release

[Herve BRANGIER]

Hi,

Do you known how to force a socket release ?

Our problem is that sometimes after a server
crash, the port is not release and we can't
restart this software. So we need to force
release of this port at system level.

Thanks

Herve

[James R. Ferguson]

Hi:

You may be faced with a reboot to clear the port.

While 'netstat -an' will show you the ports in use, you will need 'lsof' to determine what process is bound to the port.

See also, my comments in this thread:

http://my1.itrc.hp.com/cm/QuestionAnswer/1,1150,0xacfe5f260cafd4118fef0090279cd0f9,00.html

A very good discussion of what you are seeing can be found in this thread:

http://my1.itrc.hp.com/cm/QuestionAnswer/1,1150,0xdc968d77ef20d411b66300108302854d!1,00.html

...JRF...

[Craig Gilmore · Accepted solution]

James is right, you might be faced with a system reboot to clear this problem. However, you did not specify if you were running HP-UX 11.00 or 10.20.

On 10.20, the only way to clear a port in use where the application using the port did not clear it is to reboot.

However starting with 10.30 and on 11.00 you can use ndd and tcp_discon_by_addr to free up a hung TCP connected port, even if the process that owned the port is no longer running.

You will need the full IP and PORT number for both sides of the connection. This needs to be converted to a 32 byte hex number. But it usually is less intrusive than a full system reboot.

[rick jones]

sigh - i would suggest that folks not get into the habit of using the unsupported tcp_discon_mumble mechanisms to clear perceived hung ports. knuth only knows what sort of havoc it could wreak.

if an application will not restart while there are still TCP connections in various states, it indicates a bug in that application. Specifically, the application should be using setsockopt() to set SO_REUSEADDR _before_ it tries to bind() to its well-known port number.

This will allow the app to be restarted while there are still old connections laying around. The only place it will not work is if the old instance of the app is still running and still has a TCP endpoint in the LISTEN state bound to that port number.

So, don't treat the symptom, cure the disease - get the app fixed.