[Qemu-devel] For unix domain socket, will only one client could connect to this socket?

[Qemu-devel] For unix domain socket, will only one client could connect to this socket?

[Sam]

Hi all,

I'm working on qemu-qga, and I want to send qmp command from this unix
socket, but it hanged there(no response), I don't know if it's connect
failed or something?

[root@yf-mos-test-net09 ~]# socat
> /opt/cloud/workspace/servers/f6fdd093-383b-444e-9bcf-dfa81794d465/qga.sock
> readline
> {"execute": "guest-execute", "session": "4768", "arguments": {"commands":
> [{"command": "/bin/sh", "arguments": ["sh", "-c", "ping -c 1
> 172.16.0.1"]}]}}


My question is, for tcp or udp socket, many client could connect to one
server, is unix socket the same? Thank you~

Re: [Qemu-devel] For unix domain socket, will only one client could connect to this socket?

[Daniel P. Berrange]

On Thu, Jul 27, 2017 at 06:37:32PM +0800, Sam wrote:
> Hi all,
> 
> I'm working on qemu-qga, and I want to send qmp command from this unix
> socket, but it hanged there(no response), I don't know if it's connect
> failed or something?
> 
> [root@yf-mos-test-net09 ~]# socat
> > /opt/cloud/workspace/servers/f6fdd093-383b-444e-9bcf-dfa81794d465/qga.sock
> > readline
> > {"execute": "guest-execute", "session": "4768", "arguments": {"commands":
> > [{"command": "/bin/sh", "arguments": ["sh", "-c", "ping -c 1
> > 172.16.0.1"]}]}}

Pointless use of shell there. Just directly run ping

  {"command": "/bin/ping", "arguments": ["-c", "1", "172.16.0.1"]}

> 
> 
> My question is, for tcp or udp socket, many client could connect to one
> server, is unix socket the same? Thank you~

You can only ever have a single client connected, even with tcp/unix
sockets backends.

Regards,
Daniel
-- 
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Re: [Qemu-devel] For unix domain socket, will only one client could connect to this socket?

[Sam]

Thank you, I think another process connect this socket, so I hanged here.

2017-07-27 18:47 GMT+08:00 Daniel P. Berrange <berrange@redhat.com>:

> On Thu, Jul 27, 2017 at 06:37:32PM +0800, Sam wrote:
> > Hi all,
> >
> > I'm working on qemu-qga, and I want to send qmp command from this unix
> > socket, but it hanged there(no response), I don't know if it's connect
> > failed or something?
> >
> > [root@yf-mos-test-net09 ~]# socat
> > > /opt/cloud/workspace/servers/f6fdd093-383b-444e-9bcf-
> dfa81794d465/qga.sock
> > > readline
> > > {"execute": "guest-execute", "session": "4768", "arguments":
> {"commands":
> > > [{"command": "/bin/sh", "arguments": ["sh", "-c", "ping -c 1
> > > 172.16.0.1"]}]}}
>
> Pointless use of shell there. Just directly run ping
>
>   {"command": "/bin/ping", "arguments": ["-c", "1", "172.16.0.1"]}
>
> >
> >
> > My question is, for tcp or udp socket, many client could connect to one
> > server, is unix socket the same? Thank you~
>
> You can only ever have a single client connected, even with tcp/unix
> sockets backends.
>
> Regards,
> Daniel
> --
> |: https://berrange.com      -o-    https://www.flickr.com/photos/
> dberrange :|
> |: https://libvirt.org         -o-
> https://fstop138.berrange.com :|
> |: https://entangle-photo.org    -o-    https://www.instagram.com/
> dberrange :|
>

Re: [Qemu-devel] For unix domain socket, will only one client could connect to this socket?

[Daniel P. Berrange]

On Thu, Jul 27, 2017 at 07:58:06PM +0800, Sam wrote:
> Thank you, I think another process connect this socket, so I hanged here.

Yes, if another process has it open, you would see a hang if you tried
to connect to it, because the kernel will have queued the incoming
connection, but QEMU will not call accept() on it until the first client
has gone.


Regards,
Daniel
-- 
|: https://berrange.com      -o-    https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org         -o-            https://fstop138.berrange.com :|
|: https://entangle-photo.org    -o-    https://www.instagram.com/dberrange :|