> Hello all ,
>
> How can we allow a server to bind to a port that appears to be held open =y a
> client process? The netstat below indicates that port 9521 is not b=ing
> listened
> to by any server process:
>
> $netstat -an | grep 9521
> tcp 0 0 127.0.0.1:9521 =A0 127.0.0.1:9521 =A0 ESTABLISHED
> tcp 0 0 10.1.235.31:47776 =A0 10.1.19.219:9521 ESTABL=SHED
>Ok this should be in FIN_WAIT or FIN_WAIT2 or something.
>If it is connected how will the socket be free?
> We are using SO_REUSEADDR in the server code, which on Solaris always all=wed
> to re-bind to the port in question.
> int on = 1;
> if (setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(=n)) == -1)
> printf("setsockopt SO_REUSEADDR failed: port=%= fd=%d", on, fd);
>
>
> On Linux there appears to be a caveat with using SO_REUSEADDR in conjunct=on
> with INADDR_ANY. This is from the Linux socket man page:
> SO_REUSEADDR
> Indicates that the rules used in =alidating addresses supplied
> in a bind(2) call should allow re=se of local addresses. For
> PF_INET sockets this means that a=socket may bind, except when
> there is an active listening s=cket bound to the address.
> When the listening socket i= bound to INADDR_ANY with a spe-
> cific port then it is not possibl= to bind to this port for
> any local address. despite the fact that no server can bind the port, no new
> client can esta=lish a connection to the port.
> Also, the client that is established to the port is sending messages t= what
> it believes is its peer. No errors are returned. The socket has been in this
> state for couple of a days
>I know this question really really well.
Do you have solution in Linux working , it works fine in Solaris .
>I have faced this problem several times.
>But I still can't answer it. I use
>setsockopt( ... SO_REUSEADDR..)
I used the setsockopt( ... SO_REUSEADDR..) in my code , still its not working ,
still the same issue
>and
>setsockopt(...SO_REUSEPORT..)
I believe SO_REUSEPORT is not portable , its more used in BSD Unixes and i
believe that its functionality is covered by SO_REUSEADDR under linux as per
manual
I have tried couple of more options for reusing the port by setting the kernel
parameters (TCP_TW_RECYCLE and TCP_TW_REUSE) , not much luck here also .
I did do good amount of reserach online before posting , but could not get
much info to resolve
http://hea-www.harvard.edu/~fine/Tech/addrinuse.html
http://lkml.indiana.edu/hypermail/linux/kernel/9902.1/0922.html
http://stackoverflow.com/questions/3127990/linux-sockets-server-exits-before-client
https://www.ibm.com/developerworks/library/l-sockpit/
Girish once gain many thanks for providing your pointers and rellly
appriciate your time
Thanks for your inputs in advance
Thanks
Narendra
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