Error binding socket: address already in use

Error binding socket: address already in use

[Peter Lezoch]

Hi,
killing a server task that is operating on a UDP socket( AF_INET, SOCK_DGRAM, IPPROTO_UDP ), leaves the socket in an unclosed state. A subsequently started task, that wants to use the same port, gets from bind above error message.This is, in my opinion, wrong behavior, because of the connectionless nature of UDP. Only reboot solves this situation. It looks, as if in net/socket.c, TCP and UDP are handled in the same way without taking into account the different nature of the protocols?!
How can I overcome this problem ?

kind regards

peter lezoch

Re: Error binding socket: address already in use

[Jan Engelhardt]

>Hi,
>killing a server task that is operating on a UDP socket( AF_INET, 
>SOCK_DGRAM, IPPROTO_UDP ), leaves the socket in an unclosed state. A 
>subsequently started task, that wants to use the same port, gets from 
>bind above error message.This is, in my opinion, wrong behavior, 

man setsockopt
Look for SO_REUSEADDR
It is all correct behavior.

>because of the connectionless nature of UDP. Only reboot solves this 

Waiting a while should also solve this.

>situation. It looks, as if in net/socket.c, TCP and UDP are handled in 
>the same way without taking into account the different nature of the 
>protocols?!
>How can I overcome this problem ?

Jan Engelhardt
-- 

Re: Error binding socket: address already in use

[David M. Lloyd]

On Wed, 2006-09-13 at 14:41 +0000, Peter Lezoch wrote:
> Hi,
> killing a server task that is operating on a UDP socket( AF_INET, SOCK_DGRAM, IPPROTO_UDP ), leaves the socket in an unclosed state. A subsequently started task, that wants to use the same port, gets from bind above error message.This is, in my opinion, wrong behavior, because of the connectionless nature of UDP. Only reboot solves this situation. It looks, as if in net/socket.c, TCP and UDP are handled in the same way without taking into account the different nature of the protocols?!
> How can I overcome this problem ?

Perhaps SO_REUSEADDR is what you're looking for?

man 7 socket

- DML

Re: Error binding socket: address already in use

[Alan Cox]

Ar Mer, 2006-09-13 am 14:41 +0000, ysgrifennodd Peter Lezoch:
> Hi,
> killing a server task that is operating on a UDP socket( AF_INET,
> SOCK_DGRAM, IPPROTO_UDP ), leaves the socket in an unclosed state. 

For UDP the socket closes at the point the last user of the socket
closes. For TCP there is a time delay mandated by the specification.

If you are seeing UDP sockets remain open when you kill a server make
sure it hasn't forked other processes and passed them the file handle.

Re: Error binding socket: address already in use

[linux-os (Dick Johnson)]

On Wed, 13 Sep 2006, Peter Lezoch wrote:

>
> Hi,
> killing a server task that is operating on a UDP socket( AF_INET, SOCK_DGRAM, IPPROTO_UDP ), leaves the socket in an unclosed state. A subsequently started task, that wants to use the same port, gets from bind above error message.This is, in my opinion, wrong behavior, because of the connectionless nature of UDP. Only reboot solves this situation. It looks, as if in net/socket.c, TCP and UDP are handled in the same way without taking into account the different nature of the protocols?!
> How can I overcome this problem ?
>
> kind regards
>
> peter lezoch


Try:
  int opt = 1;
  setsockopt(s, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));

Cheers,
Dick Johnson
Penguin : Linux version 2.6.16.24 on an i686 machine (5592.66 BogoMips).
New book: http://www.AbominableFirebug.com/
_
\x1a\x04

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Re: Error binding socket: address already in use

[Colin Hirsch]

On Wed, Sep 13, 2006 at 04:23:35PM +0100, Alan Cox wrote:
> Ar Mer, 2006-09-13 am 14:41 +0000, ysgrifennodd Peter Lezoch:
> > Hi,
> > killing a server task that is operating on a UDP socket( AF_INET,
> > SOCK_DGRAM, IPPROTO_UDP ), leaves the socket in an unclosed state. 
> 
> For UDP the socket closes at the point the last user of the socket
> closes. For TCP there is a time delay mandated by the specification.
> 
> If you are seeing UDP sockets remain open when you kill a server make
> sure it hasn't forked other processes and passed them the file handle.

Additional note on REUSEADDR: The standard semantics of REUSEADDR on a
UDP socket is to allow several sockets to bind to the same address
simultaneously (!), i.e. if your server uses it you can start it several
times on the same socket, which is not what one normally wants.

Regards, Colin