[Simh] FTP client connecting to SIMH/OpenVMS?

Bucher Andreas A.Bucher at alcatel-lucent.de
Wed Jun 11 05:51:18 EDT 2008


Hi Peter, 

after follwing this discussion (same thing again and again ...), I begin
to understand why some emulators (like VMWare) create and use own
adapters and "local" virtual subnets to connect their virtual machines
(i.e. the emulated computers).

It just struck me: How about using vmware (player = free), create the
VMWare adapter and network, and attach simh to it   (this would be an
alternative to the linux tun/tap devices) !?

Until now, I was running simh on a machine where I also have VMWare with
the virtual networks installed, and since I have enough computers
around, I never had the immediate need to connect from the host to the
emulated VAX. For working locally (e.g. laptop), I use the emulated DZ
device and attach a telnet session there (since this telnet is attached
to simh, which emulates the device, the VAX sees it as serial
connection, and there's no network problem). So, simh was running
attached to physical ("local area connection") interface of the PC,
where it was reachable from the "outside world".

Now I did the following:
- start up simh
- CTRL-E to stop startup
- sho xq eth  to list the available adapters
- the VMWare adapter stuff shows up, I note the device name (eth1 in my
case)
- attach xq eth1
- (update the VAX.INI to attach to eth1)
- start up the VAX
- Modify the IP address to use one of the 192.168... range of the VMWare
network
- Restart UCX

and now I can telnet to the emulated VAX from the host computer !


So, the trick could be to use the VMWare virtual network and attach simh
there.

Hope this helps ! Could you give it a try ?

regards,
Andreas

 

> -----Original Message-----
> From: simh-bounces at trailing-edge.com 
> [mailto:simh-bounces at trailing-edge.com] On Behalf Of Peter Moreton
> Sent: Mittwoch, 11. Juni 2008 10:31
> To: simh at trailing-edge.com
> Subject: [Simh] FW: FW: FTP client connecting to SIMH/OpenVMS?
> 
> 	Thanks for that insight Brad (and others). FYI, the 
> issue affects XP as well as Linux. Now I am aware of the 
> issue, I can work by using a PC on the LAN as a client and a 
> PC on the LAN running SIMH, instead of both Client and SIMH 
> on the same machine. Of course this means I cannot now 
> develop client-server apps on one laptop while commuting on 
> train, but hey.... 
> 	
> 	
> 	 
> 	
> ________________________________
> 
> 
> 	> From: brad at heeltoe.com
> 	> To: jeremy at vsm.com.au
> 	> CC: petermoreton at hotmail.co.uk; simh at trailing-edge.com
> 	> Subject: Re: [Simh] FW: FTP client connecting to 
> SIMH/OpenVMS? 
> 	> Date: Tue, 10 Jun 2008 20:01:00 -0400
> 	> 
> 	> 
> 	> Jeremy Begg wrote:
> 	> >Peter,
> 	> >
> 	> >>I just found that I *can* FTP and Telnet into the 
> VMS machine from
> 	> >>another Physical host on the LAN - so it seems as 
> though TCP/IP traffic
> 	> >>between VMS and the PC running SIMH isn't routing, 
> but so long as I
> 	> >>connect to the VMS machine from another PC on the 
> LAN, then the VAX
> 	> >>responds as it should.
> 	> >
> 	> >I believe this is a known problem with SIMH 
> (actually I believe it's a
> 	> >problem in the underlying networking library used by 
> SIMH). To
> 	> >communicate between the host PC and the emulated 
> VAX, the host PC
> 	> >needs to have an ethernet NIC which is dedicated to the VAX.
> 	> 
> 	> if simh is running on linux, it's a long standing 
> issue with linux (and
> 	> possibly every other unix)
> 	> 
> 	> Depending on what sort of network "tap" you use to 
> simulate the ethernet
> 	> you may not be able to access the simulated host from 
> the host machine.
> 	> You can, however, access it from any other host on 
> the network.
> 	> 
> 	> I figured out exactly what the issue was years ago 
> and asked the linux
> 	> networking community about it - the response was that 
> most people didn't
> 	> notice or care and fixing it was hard.
> 	> 
> 	> It happens more and more now that people are doing 
> emulators as machines
> 	> get faster. I've run into before. I think I got 
> around it last by
> 	> using an IP level tap internet (i.e. creating a new 
> interface) but that
> 	> has it's own set of issues.
> 	> 
> 	> I as I recall (dimly), if you use an ethernet level 
> tap, the ethernet
> 	> driver has to duplicate each packet sent and pass 
> them back up to the
> 	> simulator socket. Likewise, all packets received have 
> to be duplicated
> 	> and sent to the simulator socket. I think right now 
> the receive side
> 	> happens but not the transmit side.
> 	> 
> 	> Typing it here is seems simple to fix but it didn't 
> look easy at the
> 	> time. Ah yes. the problem is you also want to send 
> packets back to the
> 	> host if they originated in the sim. but you don't 
> know who sent them in
> 	> the ethernet driver (very low level). so you risk 
> sending packets back
> 	> to the host which originated in the host and packets 
> back to the sim
> 	> which originated in the sim.
> 	> 
> 	> basically, you want to simulate a mini ethernet wire. 
> I guess you
> 	> could do some sort of simple learning bridge.
> 	> 
> 	> Hopefully this illustrates the problem and some of 
> the complexity.
> 	> 
> 	> anyway, simh suffers this problem as do many emulators.
> 	> 
> 	> -brad
> 	> 
> 	
> 	
> 	
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