Serial port over TCP/IP

Serial port over TCP/IP

[Michael Buesch]

Hi.

Is it possible to make a char-dev (a serial device ttyS0)
available via TCP/IP on a network like it is possible
for block-devices like a harddisk via nbd?
Is kernel-support for this present?
If not, is it technically possible to develop such a driver?

Thanks.
Regards Michael Buesch.

-- 
My homepage: http://www.8ung.at/tuxsoft
fighting for peace is like fu**ing for virginity

Re: Serial port over TCP/IP

[Dr. David Alan Gilbert]

* Michael Buesch (freesoftwaredeveloper@web.de) wrote:
> Hi.
> 
> Is it possible to make a char-dev (a serial device ttyS0)
> available via TCP/IP on a network like it is possible
> for block-devices like a harddisk via nbd?
> Is kernel-support for this present?
> If not, is it technically possible to develop such a driver?

I keep thinking that it would be nice to have a mechanism for user space
char devices; it would have to have a mechanism to pass all the ioctls
to the process that dealt with it.

(The particular cases which sparked this idea for me were to do user
space SCSI tape drivers to do raid tape and the like, and for emulation
of touch screens or mice on systems that only had the other.).

Dave
 ---------------- Have a happy GNU millennium! ----------------------   
/ Dr. David Alan Gilbert    | Running GNU/Linux on Alpha,68K| Happy  \ 
\ gro.gilbert @ treblig.org | MIPS,x86,ARM,SPARC,PPC & HPPA | In Hex /
 \ _________________________|_____ http://www.treblig.org   |_______/

Re: Serial port over TCP/IP

[Rob van Nieuwkerk]

Michael Buesch wrote:
> Is it possible to make a char-dev (a serial device ttyS0)
> available via TCP/IP on a network like it is possible
> for block-devices like a harddisk via nbd?
> Is kernel-support for this present?
> If not, is it technically possible to develop such a driver?

Hi Michael,

No need for kernel support.  This simple shell-script is what I use for
a project at the moment.

	greetings,
	Rob van Nieuwkerk

------------------------------------------------
#!/bin/sh

TCP_PORT=4000
SERIAL_PORT=/dev/ttyS1
BAUDRATE=19200

while (true)
	do
	(stty $BAUDRATE -echo clocal raw pass8 ; exec nc -l -p $TCP_PORT) \
		< $SERIAL_PORT > $SERIAL_PORT
done
------------------------------------------------

Re: Serial port over TCP/IP

[Michael Buesch]

On Sunday 06 April 2003 15:11, Dr. David Alan Gilbert wrote:
> I keep thinking that it would be nice to have a mechanism for user space
> char devices; it would have to have a mechanism to pass all the ioctls
> to the process that dealt with it.

But wouldn't this make too much overhead, if implemented all in userspace?
I say this, because nbd is also implemented in user- und kernel-space.

Regards Michael Buesch. 

-- 
My homepage: http://www.8ung.at/tuxsoft
fighting for peace is like fu**ing for virginity

Re: Serial port over TCP/IP

[Michael Buesch]

On Sunday 06 April 2003 15:35, Rob van Nieuwkerk wrote:
> No need for kernel support.  This simple shell-script is what I use for
> a project at the moment.
> [...]

thanks. :)

Regards Michael Buesch.

-- 
My homepage: http://www.8ung.at/tuxsoft
fighting for peace is like fu**ing for virginity

Re: Serial port over TCP/IP

[Dr. David Alan Gilbert]

* Michael Buesch (freesoftwaredeveloper@web.de) wrote:
> On Sunday 06 April 2003 15:11, Dr. David Alan Gilbert wrote:
> > I keep thinking that it would be nice to have a mechanism for user space
> > char devices; it would have to have a mechanism to pass all the ioctls
> > to the process that dealt with it.
> 
> But wouldn't this make too much overhead, if implemented all in userspace?
> I say this, because nbd is also implemented in user- und kernel-space.

Sure it would have overhead; but it would be a general mechanism and
mean that the kernel didn't need lots of char drivers (except for boot
time things). Lots of devices are really just filters/wrappers over
other more basic devices (look at the growing pile of USB serial
device drivers).  Most char devices have such a low throughput that the
little overhead wouldn't make much difference, but would simplify the
kernel.

Dave
 ---------------- Have a happy GNU millennium! ----------------------   
/ Dr. David Alan Gilbert    | Running GNU/Linux on Alpha,68K| Happy  \ 
\ gro.gilbert @ treblig.org | MIPS,x86,ARM,SPARC,PPC & HPPA | In Hex /
 \ _________________________|_____ http://www.treblig.org   |_______/

Re: Serial port over TCP/IP

[Michael Buesch]

On Sunday 06 April 2003 23:12, Jeff Randall wrote:
> On Sun, Apr 06, 2003 at 10:47:45PM +0200, Michael Buesch wrote:
> > On Sunday 06 April 2003 22:14, Jeff Randall wrote:
> > > Yes, it would be very possible to do.
> >
> > Yes, but after Rob posted this script
> >[...]
> > do you think it's still neccessary to develop a driver?
> > I don't think so.
>
> Depends what kind of flexiblity you want.  If you have no need to support
> IOCTL's remotely, that script is probably sufficient.

Hm, that's the point. I don't know if ioctls are needed, because I'm not the
user of this "network COM-port", but only the possible developer. :)
I'll ask the person, who requested this feature tomorrow.

I think ioctls might be needed for his application. But the simple
nc-script doesn't provide them.

One thing is clear: For server-side there is no need for kernel-support.
But for the client kernel-support might be the best solution.

Regards Michael Buesch.

-- 
My homepage: http://www.8ung.at/tuxsoft
fighting for peace is like fu**ing for virginity

Re: Serial port over TCP/IP

[H. Peter Anvin]

Followup to:  <200304061447.46393.freesoftwaredeveloper@web.de>
By author:    Michael Buesch <freesoftwaredeveloper@web.de>
In newsgroup: linux.dev.kernel
> 
> Is it possible to make a char-dev (a serial device ttyS0)
> available via TCP/IP on a network like it is possible
> for block-devices like a harddisk via nbd?
> Is kernel-support for this present?
> If not, is it technically possible to develop such a driver?
> 

I think what you need is the enhanced pty driver patch which was
posted recently, which made is possible for a user-space process to
also capture ioctls() such as baud rate setting etc.  Then the rest of
the work can be done in userspace.

	-hpa

-- 
<hpa@transmeta.com> at work, <hpa@zytor.com> in private!
"Unix gives you enough rope to shoot yourself in the foot."
Architectures needed: ia64 m68k mips64 ppc ppc64 s390 s390x sh v850 x86-64

Re: Serial port over TCP/IP

[Michael Buesch]

On Monday 07 April 2003 04:37, H. Peter Anvin wrote:
> I think what you need is the enhanced pty driver patch which was
> posted recently, which made is possible for a user-space process to
> also capture ioctls() such as baud rate setting etc.  Then the rest of
> the work can be done in userspace.

Thanks, this is a good solution!

Regards
Michael Buesch

-- 
My homepage: http://www.8ung.at/tuxsoft
fighting for peace is like fu**ing for virginity