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From: "PAULUS, Raimund, TI-ABN" <Raimund DOT Paulus AT dillinger DOT biz>
To: "'cygwin AT cygwin DOT com'" <cygwin AT cygwin DOT com>
Subject: Re: RPC clnt_create() adress already in use
Date: Wed, 27 Sep 2017 12:50:48 +0000
Message-ID: <59D90AF8D70E9740907BACDE2BCB52083662AC7B@RESW102.resdom01.local>
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Hello Mark,

i compiled and linked just as you.
As i mentioned in an other email, if I use socket-connections in the same manner with a socket-service, in don't need to setsockopt(.., SO_REUSEADDR, ...) and it works.

Raimund


-----Ursprüngliche Nachricht-----
Von: cygwin-owner AT cygwin DOT com [mailto:cygwin-owner AT cygwin DOT com] Im Auftrag von Mark Geisert
Gesendet: Mittwoch, 27. September 2017 11:50
An: cygwin AT cygwin DOT com
Betreff: Re: RPC clnt_create() adress already in use

Hello Raimund,
Let's keep this on the mailing list please.

PAULUS, Raimund, TI-ABN wrote:
> Hallo Mark Geisert,
>
> many thanks for your answer. I supposed this too.
>
> I included in my source code the following function calls after clnt_create():
>
> int fd = 0;
> bool bool_ret = clnt_control(cl, CLGET_FD, &fd); if(bool_ret == true) {
>   printf("fd: %d\n", fd);
>
>   int enable = 1;
>   retval = setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &enable, sizeof(int));
>   if(retval < 0)
>     fprintf(stderr, "Fehler setsockopt(): %s\n", strerror(errno)); }
>
> The function clnt_control() delivers the socket of the RPC-Client-Handle.
> The result is the same as before. Moreover i think, the effect of setsockopt() would be valid only during the process is running (my test scenarios 1 and 2).
> But it wouldn't change anything regarding my test scenario 3 (several restarts).
>
> Raimund

I looked through the libtirpc source code and nowhere is SO_REUSEADDR being set. 
  You are on the right track with how to do it, but by the time clnt_create() returns to you it is already too late.  As far as I can tell there is no way to get access to the socket between the time it's created within libtirpc and the time it's made available to you by clnt_create().

I did try running your testcase (thanks for supplying that) but I don't have a local machine running RPC services and don't wish to poke at random machines on the Internet ;-).  I had to compile it as so:
     gcc -g -o test_rpc -I/usr/include/tirpc test_rpc.c -ltirpc You are taking care to compile against the correct RPC-package includes and link against the correct RPC-package libraries, yes?

Speculation: There might be a way to decompose what clnt_create() does into other libtirpc functions that accomplish the same thing, but in smaller pieces such that you could set the socket option before bind() is called.  That would be a fair amount of work though and given my cursory look at the source I don't know if it's even possible.

..mark

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