topic Re: Passing socket/file descriptors between processes? in Operating System - OpenVMS

Passing socket/file descriptors between processes?

Martin Cowie — Thu, 03 Mar 2005 11:56:35 GMT

I'm unsure if the answers I'll get to this question will be all that polite, as this is pretty high octane stuff on Unix =)

Can I pass a socket descriptor from a parent process to a child process on VMS? By "passing a descriptor descriptor" I mean actually passing the ownership of the socket from one process to another - a little more that writing a 4 byte integer down a pipe.

Traditionally BSD and and SysV employ different approaches of achieving this, but both of them rely on a pipe between the two processes.

Does anyone know if the C RTL supports either mechanism, should I look into using the underlying system services, or give up altogether?

My thanks again for your headscratching,

M.

Re: Passing socket/file descriptors between processes?

Ian Miller. — Thu, 03 Mar 2005 12:35:09 GMT

the full fork semantics are not implemented on VMS (its being thought about).

does vfork do what you want?
See
http://h71000.www7.hp.com/commercial/c/docs/5763pro_047.html#index_x_1307
and
http://h71000.www7.hp.com/commercial/c/docs/5763pro_064.html#index_x_1727

Re: Passing socket/file descriptors between processes?

Bojan Nemec — Thu, 03 Mar 2005 13:21:56 GMT

Martin,

In this Ask the Wizard you have an example on how to pass a socket to a subprocess:

http://h71000.www7.hp.com/wizard/wiz_3995.html

Bojan

Re: Passing socket/file descriptors between processes?

Martin Cowie — Fri, 04 Mar 2005 09:36:05 GMT

I should really be more specific - I'm looking to find out how a socket can be passed from a parent to a child process, *after* the vfork/exec combination.

Re: Passing socket/file descriptors between processes?

Bojan Nemec — Fri, 04 Mar 2005 09:53:33 GMT

Martin,

The example in the link in my previous post does yust that. Unfortunately it is writen in the $qio interface to sockets, which is more difficult to understand for an Unix guy.

In short:
The example (PARENT.C) listen for an incoming connection, when the connection is established creates a subprocess (CHILD.C) calling lib$spawn and pass the socket to it (using a mailbox). Then this subprocess comunicates with the client on that socket.

Probably the line
$DESCRIPTOR(command, "run serverc_qio2");
should be
$DESCRIPTOR(command, "run child");

Bojan

Re: Passing socket/file descriptors between processes?

Vouters — Sat, 02 Apr 2005 03:31:59 GMT

Does http://h18000.www1.hp.com/support/asktima/operating_systems/009D3F45-215FE900-1C0186.html
would make the trick ?
Philippe