Remote Access to NMR Workstations

The UNIX workstations which control the Varian NMR spectrometers are connected to the campus network, to allow data transfer to other computers, remote monitoring, and backups.

• alvis.chem.uregina.ca controls the Varian Mercury 300 MHz in LB311

To minimize the risk of break-ins by cyber-vandals, a “firewall” restricts the data flowing into and out of the NMR workstations. These restrictions complicate communications with the NMR, but inconvenience is the price of security.

Technically inclined readers may be satisfied with the following summary of the firewall configuration:

• The only incoming connections accepted are those using the secure shell protocol, version 2 (SSH2).
• Incoming connections are accepted only from a limited set of machines, essentially any IP number in uregina.ca as well as some which might be used by Varian technicians.
• Outgoing HTTP, HTTPS, DNS, FTP and SSH connections are permitted to allow web surfing and remote logins.
• No provision exists for transmitting or receiving email on the NMR workstations.

This rest of this document provides more detail about software you can use to connect to the NMR workstations as well as instructions for some typical activities:

• File Transfers to and from PCs on campus
• Remote logins from PCs on campus
• Access from off-campus
• File Transfers to and from UNIX machines on campus
• Remote logins from UNIX machines on campus
• Providing remote graphical access using VNC

Access from PCs on campus

File Transfers to and from Windows PCs on campus, using WinSCP

You might be accustomed to copying files between computers using the FTP File Transfer Protocol, but because FTP is not encrypted, the firewall does not permit FTP connections to the NMR workstations.

So to transfer data, you need some utility that copies files via the secure shell protocol, and you need to connect from a computer that the firewall trusts.

The most straightforward way to transfer files between the NMR workstations and a Windows PC on campus is with the Secure Copy Client, WinSCP. If WinSCP is not already installed on your PC, you can download a copy preconfigured for use at the U of R from the UR Configured Software Suite, or you can look for a more recent release from the WinSCP home.

WinSCP provides a graphical interface for transferring files, similar to that provided by WinFTP. Here, for example, is what appears when you start the UR Configured WinSCP by selecting Programs→Urcomm→Secure Copy Client from the Windows Start menu, and then fill in the information required to connect to the Mercury 300 MHz workstation on WinSCP's Basic tab. Use the same userid and password as you do when sitting in front of the NMR.

After you click Login, you may see a scary message about the server's host key not being cached in the registry, which just means that nobody has ever connected to the workstation from your PC before. If you continue the connection, you'll see a panel that looks something like this (assuming that your WinSCP preferences remain set to the “Norton Commander” interface):

The left side of the panel shows files on the PC while the right side shows files on the NMR workstation. You can navigate through the filesystem by clicking on directory icons, as you are accustomed to doing in Windows. Dragging file icons from one side of the display to the other causes the files to be copied between machines; a dialog box prompts you for the attributes to be used for the newly created file. Or you can simply double click an icon to copy its file to the opposite side using default attributes.

(WinSCP has an alternate “Explorer-like” interface which shows only a single directory on the remote machine, but that view makes it harder to distinguish local from remote files).

Remote logins from a PC on campus

To login to the NMR workstations from your PC, you'll need to install a terminal emulator capable of SSH2. PuTTY is a freely available possibility. PuTTY provides lots of configuration options for you to explore, but you can log in simply by running the putty program, filling in the initial screen as indicated below (be sure to click the SSH protocol choice instead of the Telnet default) and clicking Open.

PuTTY will bring up a terminal window where you will be prompted for your userid and password on the NMR workstation.

Access from machines off campus

Many people with email access at the University of Regina have a UNIX account on telnet.uregina.ca. Many have access to other UNIX machines as well. This allows access to the NMR workstations from machines which the firewall does not trust using a simple, albeit inconvenient, trick: communicate in two hops through an intermediate UNIX machine on campus (where you use the techniques described in the next section).

Let's say you want to copy the file periodic.tbl from your PC at home to mesmer for a future experiment and also copy the file elements.dat from mesmer for analysis on your PC. Here's one approach:

1. Use WinSCP to copy periodic.tbl from your PC to telnet.uregina.ca (or some other machine on campus to which you have access).
2. Use PuTTY or TeraTerm to log into telnet.uregina.ca from your PC.

3. From telnet.uregina.ca use sftp to copy periodic.tbl to mesmer.engg.uregina.ca, and then to copy elements.dat from mesmer to telnet.

   (It is possible to avoid the double copy by setting up an an SSH “tunnel” through the intermediate machine, but that requires some potentially confusing configuration steps; look for references to tunnels in the documentation for your SSH program if you wish to explore this option.)

4. Use WinSCP to copy elements.dat from telnet.uregina.ca to your PC.

Access from UNIX/LINUX machines on campus

File Transfers to and from UNIX machines on campus, using sftp or scp

sftp

sftp provides an interface similar to the ftp command, but uses SSH2 for communication.

Here's a sample session, where you log into alvis as user myname from a machine called aufbau. Then you copy a file named fid from the test.fid subdirectory of your home directory on alvis to your current directory on aufbau and copy some.file from the current directory on aufbau to your test.fid directory on alvis. Bold face distinguishes the commands you would type from the prompts the computer prints:

If you type help at the sftp prompt, it responds with a list of all of its commands.

scp

scp works like the normal UNIX file copy command cp, except that you can prefix a filename with a machine name followed by a colon, to indicate that the file is on another computer. Here is an example of copying the file fid from the test.fid subdirectory of your home directory on alvis to the directory dest on a machine named aufbau.

(There may still be a few UNIX machines on campus where the scp command defaults to version 1 of the SSH protocol. These machines provide version 2 with the command scp2).

If your userid is different on the two machines, you can include the remote userid before the remote machine name, separated by an at-sign:

If the remote files are not in your home directory, you can specify a complete path beginning with the root directory:

You can copy all the contents of a directory with scp's -r (for “recursive”) option:

Remote logins from a UNIX/LINUX machine on campus

To log into an NMR workstation from a UNIX computer on campus, just run the ssh command, supplying your userid on the NMR workstation together with its hostname:

Enter your password when prompted for it, and you will be logged in.

(There may still be a few UNIX machines on campus where the ssh command defaults to version 1 of the SSH protocol. These machines provide version 2 with the command ssh2.)

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