Need tips to open a socket and to debug it

Need tips to open a socket and to debug it

[Glen L]

Greetings all,

I'm moving a "C" program to 64-bit Windows 10 that worked previously in 32-bit Win7. It builds, compiles and runs (AFAIK) with the exception of being able to open a socket. Calling the socket thusly:

    if ((g->listen = socket(PF_LOCAL, SOCK_STREAM, 0)) < 0) {
        fprintf(stderr, "Can't create socket: %d %s", (int) errno, strerror(errno));
        return -1;
    }

The code is built for 64-bit windows using this:
x86_64-pc-cygwin-gcc -g --std=gnu99 -O0 -DGLUT_DISABLE_ATEXIT_HACK -nostdinc -march=core2 -m64


The result, however, is ENOENT  and "No such file or directory."
uname -a : CYGWIN_NT-10.0 LAPTOP-B8KN061R 2.4.0(0.293/5/3) 2016-01-15 16:16 x86_64 Cygwin

I've tried a few things with the firewall and looked for internet tips. No luck, clearly.

So, I had the idea to step into the socket call and see what's going on. ENOENT seems a bit weird. I'm using Eclipse and gdb for this and it's working fine, with source, for the application. I can step around the machine code for the cygwin calls but no source. I've tried downloading the source files and debug info but I'm perplexed as to making that work. I don't seem to be finding the source files by hand that look like the machine code.

Can someone point me to a good reference on how to debug the distributed cygwin libraries? I would seem to be supported but I'm just not getting how to point to the sources and debug info from gdb.

Thanks for any and all support.

Glen

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Re: Need tips to open a socket and to debug it

[Corinna Vinschen]

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On Jan 16 18:16, Glen L wrote:
> 
> Greetings all,
> 
> I'm moving a "C" program to 64-bit Windows 10 that worked previously
> in 32-bit Win7. It builds, compiles and runs (AFAIK) with the
> exception of being able to open a socket. Calling the socket thusly:
> 
>     if ((g->listen = socket(PF_LOCAL, SOCK_STREAM, 0)) < 0) {
>         fprintf(stderr, "Can't create socket: %d %s", (int) errno, strerror(errno));
>         return -1;
>     }
> 
> The code is built for 64-bit windows using this:
> x86_64-pc-cygwin-gcc -g --std=gnu99 -O0 -DGLUT_DISABLE_ATEXIT_HACK -nostdinc -march=core2 -m64
> 
> 
> The result, however, is ENOENT  and "No such file or directory."
> uname -a : CYGWIN_NT-10.0 LAPTOP-B8KN061R 2.4.0(0.293/5/3) 2016-01-15 16:16 x86_64 Cygwin
> 
> I've tried a few things with the firewall and looked for internet
> tips. No luck, clearly.

There's no firewall involved if a simple socket call goes wrong.
For AF_LOCAL Cygwin opens an AF_INET socket, but which is unbound
until you call bind or connect.

I tried this myself and it works for me:

  $ uname -srvm
  CYGWIN_NT-10.0 2.4.0(0.293/5/3) 2016-01-15 16:16 x86_64
  $ cat <<EOF > sock.c
  #include <sys/types.h>          /* See NOTES */
  #include <sys/socket.h>
  #include <errno.h>
  #include <stdio.h>
  #include <string.h>

  int main()
  {
    int fd = socket (AF_LOCAL, SOCK_STREAM, 0);
    if (fd < 0)
      {
	fprintf (stderr, "Can't create socket: %d %s", errno, strerror (errno));
	return -1;
      }
    printf ("Success\n");
    return 0;
  }
  EOF
  $ gcc -g -o sock sock.c
  $ ./sock
  Success

> So, I had the idea to step into the socket call and see what's going
> on. ENOENT seems a bit weird. I'm using Eclipse and gdb for this and
> it's working fine, with source, for the application. I can step around
> the machine code for the cygwin calls but no source. I've tried
> downloading the source files and debug info but I'm perplexed as to
> making that work. I don't seem to be finding the source files by hand
> that look like the machine code.

You don't need to install the source package.  When you installed the
cygwin-debuginfo file, the debug files are installed into /usr/lib/debug/
and the sources under /usr/src/debug/cygwin-2.4.0-1/


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

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Re: Need tips to open a socket and to debug it

[Henri]

Corinna Vinschen <corinna-cygwin <at> cygwin.com> writes:

> There's no firewall involved if a simple socket call goes wrong.
> For AF_LOCAL Cygwin opens an AF_INET socket, but which is unbound
> until you call bind or connect.

s/AF_INET/AF_UNIX/ ????? (sorry for my intrusion)

Regards,
Henri


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Re: Need tips to open a socket and to debug it

[Corinna Vinschen]

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On Jan 18 18:10, Henri wrote:
> Corinna Vinschen <corinna-cygwin <at> cygwin.com> writes:
> 
> > There's no firewall involved if a simple socket call goes wrong.
> > For AF_LOCAL Cygwin opens an AF_INET socket, but which is unbound
> > until you call bind or connect.
> 
> s/AF_INET/AF_UNIX/ ????? (sorry for my intrusion)

AF_UNIX == AF_LOCAL.  Not available on Windows so needs emulation.
The emulation uses local-only AF_INET sockets.


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

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Re: Need tips to open a socket and to debug it

[Henri]

Corinna Vinschen <corinna-cygwin <at> cygwin.com> writes:

> 
> On Jan 18 18:10, Henri wrote:
> > Corinna Vinschen <corinna-cygwin <at> cygwin.com> writes:
> > 
> > > There's no firewall involved if a simple socket call goes wrong.
> > > For AF_LOCAL Cygwin opens an AF_INET socket, but which is unbound
> > > until you call bind or connect.
> > 
> > s/AF_INET/AF_UNIX/ ????? (sorry for my intrusion)
> 
> AF_UNIX == AF_LOCAL.  Not available on Windows so needs emulation.
> The emulation uses local-only AF_INET sockets.

You are correct ... I simply misread your communication.

What POSIX refers to as AF_LOCAL, and SUSv3 refers to as AF_UNIX, is
an 'Unix Domain socket' ... and of course, that type of socket needs
to be emulated on Windows.

Clear. Sorry for the noise ...

Henri


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Re: Need tips to open a socket and to debug it

[Corinna Vinschen]

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On Jan 19 08:48, Henri wrote:
> Corinna Vinschen <corinna-cygwin <at> cygwin.com> writes:
> > On Jan 18 18:10, Henri wrote:
> > > Corinna Vinschen <corinna-cygwin <at> cygwin.com> writes:
> > > 
> > > > There's no firewall involved if a simple socket call goes wrong.
> > > > For AF_LOCAL Cygwin opens an AF_INET socket, but which is unbound
> > > > until you call bind or connect.
> > > 
> > > s/AF_INET/AF_UNIX/ ????? (sorry for my intrusion)
> > 
> > AF_UNIX == AF_LOCAL.  Not available on Windows so needs emulation.
> > The emulation uses local-only AF_INET sockets.
> 
> You are correct ... I simply misread your communication.
> 
> What POSIX refers to as AF_LOCAL, and SUSv3 refers to as AF_UNIX, is
> an 'Unix Domain socket' ... and of course, that type of socket needs
> to be emulated on Windows.
> 
> Clear. Sorry for the noise ...

No worries, it's better asking if something's unclear.


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

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