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Re: Bind several times to the same port in Mac OS X

Subject: Re: Bind several times to the same port in Mac OS X
From: Timothy Wall <email@hidden>
Date: Fri, 17 Dec 2004 16:53:49 -0500
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Normally this is controlled by setsockopt with SO_REUSEADDR and (on some BSD-based systems, OSX included) SO_REUSEPORT.

You might use getsockopt in your C++ program to see how these options are set, e.g.

int inuse; int result = getsockopt(socket_fd, SOL_SOCKET, SO_REUSEADDR, (char*)&inuse, sizeof(inuse));

I believe the winsock default lets you do multiple binds (with undefined results), while most *nix make the bind exclusive by default. Last I tested OSX requires both ADDR and PORT be set in order to reuse a UDP port (e.g. for multicast).

On Dec 14, 2004, at 4:08 PM, Jesse Wilson wrote:

Dan Creswell kindly pointed me to a similar thread on this list,
"ServerSocket on Mac OS X" which was solved by using IPv4 instead of
IPv6:
    http://lists.apple.com/archives/java-dev/2004/Dec/thrd2.html
Unfortunately NIO still allows me to bind multiple times using IPv4.
For example, I've written a simple program that binds to IPv4 port
50505 twice. Here's what netstat has to say:
slackette:jessewilson$ netstat -a Active Internet connections (including servers) Proto Recv-Q Send-Q Local Address Foreign Address (state) tcp4 0 0 *.50505 *.* LISTEN tcp4 0 0 *.50505 *.* LISTEN

This is really wacky, but I'm making progress. Does anybody else have any ideas?
Thanks in advance,
Jesse Wilson
http://publicobject.com/glazedlists/
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Follow-Ups:
- Re: Bind several times to the same port in Mac OS X
  - From: Jesse Wilson <email@hidden>

References:
	>Bind several times to the same port in Mac OS X (From: Jesse Wilson <email@hidden>)
	>Re: Bind several times to the same port in Mac OS X (From: Dan Creswell <email@hidden>)
	>Re: Bind several times to the same port in Mac OS X (From: Jesse Wilson <email@hidden>)

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