Message from discussion Socket woes

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From: Eric Sosman <eric.sos...@sun.com>
Newsgroups: comp.lang.java.help
Subject: Re: Socket woes
Date: Wed, 30 Mar 2005 17:20:49 -0500
Organization: Sun Microsystems Corporation
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David F wrote:
> Howdy -
> 
> I have a client program that throws the following exception:
> Address already in use: connect
> java.net.BindException: Address already in use: connect
> 
> This client rapidly creates socket connections in a loop for stress
> testing the server.  The server works great!  :)  I didn't expect
> the client to break tho.  The last test I did, the client looped
> about 4200 times on the first run, 810 times when run a few seconds
> later, then about 4200 times after waiting a few minutes.
> 
> I suspect it's a garbage collection problem.  Could my program be
> consuming sockets faster than the garbage collector cleans them 
> up?

    It seems more likely that you're consuming port numbers
faster than TCP/IP can recycle them.  After a socket is
closed the port number remains unavailable for a time (four
minutes "by statute," IIRC, although it's fairly common for
Web servers to use shorter intervals); this is to allow time
for stale packets to expire from the network.  (You wouldn't
want a packet that had been temporarily trapped in a routing
loop to escape and disrupt a new unrelated connection that
happened to use the same port number ...)

    See java.net.Socket#setReuseAddress(boolean).

-- 
Eric.Sos...@sun.com