Making serial ports available over the net

rossmcm
rossmcm used Ask the Experts™
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I have a gadget made by Moxa called an Nport server, which makes 4 COM ports available on any machine on the local network.  The thing has an IP address in the private IP area .

The question:.  If I have a serial device connected to this thing, how much else is needed to access that thing from a PC elsewhere on the net.  Say there is an app that normally talks direct to the serial device via COM1 - instead I want to run the app elsewhere and still make it look at though the serial device is connected to it.

Do I need more hardware or am I just a few mouseclicks away?  I obviously can't go half-way around the world and expect to be able to find the thing at 192.168.0.xx on another PC.

I can do this on the local network - the NPort thingy comes with software that finds the private IP address and connects to the ports on another PC on it.   You can then map those ports to (say) COM10..COM13.

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Commented:
Typically if it is a terminal type application you would just telnet to the IP address associated with the serial port on your NPort device.  However, if you need an app to redirect to an IP address, you may have to find some software that allows you to redirect your COM ports to an IP address.  Have you tried looking at CNet yet?
Ben DaltonDirector, Integrated Systems

Commented:
I believe that this device functions in two ways. It can provide access to a simple serial device through telnet sessions directed at the assigned IP address or provide point to point access between two physical serial devices.  The latter requires a second nport. The scenario would be:

-Your PC's serial port connected to an nport
-The nport connected to an internet connection
-The second remote nport connected to an internet connection
-The remote nport connected to serial device(s)

The result is that the application on your pc accesses the local serial port as usual and sees the remote serial device as locally connected.

This device may be available with a virtual comm port driver that would allow windows apps to communicate to the remote nport through the internet as if they are connected locally. Generally this is only useful if the app is using windows APIs. Unfortuneately , lots of apps that make serial connections require dedicated access to a true serial port (that is the scenario described above)

The IP address is changeable by the way. Do you have software for the device?

Visit www.bb-elec.com  B&B Electronics sells this device and provides software and docs.

Author

Commented:
Here's the (desired) scenario:

LAN 1 has an NPort unit plugged into the ethernet port, IP address 192.168.0.10.  The NPort unit has a serial device plugged into one of its COM ports.

LAN 1 also has a dedicated Internet wireless connection, fixed IP 210.54.179.219.  The Internet box is 192.168.0.1 and runs ZoneAlarm.

A PC elsewhere on the web runs NPort Lite manager.  It runs a well-behaved Windows app that uses API calls to communicate with the COM ports.  Normally the serial device plugs directly into the COM port of the PC running the app, but in this scenario, the PC running the app and the serial device are separated and connected only by the web.

I can get it running no problem when the PC running the app is on the same LAN - then NPort Lite Manager can find the NPort unit on the network.

How easy is it to get it working when the PC is remote?  How do I Telnet to an IP address that is private to a LAN?

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Ben DaltonDirector, Integrated Systems

Commented:
Gotcha...  How are you routing internet traffic? The solution here is to determine the specific ports used by the NPort and redirect those at the router to 192.168.0.10.

Author

Commented:
Pass....  We just have a network card in the Internet box that connects to the wireless modem - an IPCONFIG at the internet box gives:

0 Ethernet adapter :

        IP Address. . . . . . . . . : 0.0.0.0
        Subnet Mask . . . . . . . . : 0.0.0.0
        Default Gateway . . . . . . :

1 Ethernet adapter :

        IP Address. . . . . . . . . : 169.254.109.194
        Subnet Mask . . . . . . . . : 255.255.0.0
        Default Gateway . . . . . . :

2 Ethernet adapter :

        IP Address. . . . . . . . . : 192.168.0.1
        Subnet Mask . . . . . . . . : 255.255.255.0
        Default Gateway . . . . . . :

3 Ethernet adapter :

        IP Address. . . . . . . . . : 210.54.179.219
        Subnet Mask . . . . . . . . : 255.255.255.248
        Default Gateway . . . . . . : 210.54.179.222

I'm not sure what #1 is.  #3 is presumably the NIC that talks to the wireless modem.  #2 is the NIC that talks to the LAN hub
Ben DaltonDirector, Integrated Systems

Commented:
When using NT/2K as a router, I don't think I've ever seen an option to redirect incoming port traffic.  I think you would need either a dedicated router or additional software to do the job.

How many users do you have accessing the internet?  If you can justify the cost, I would recommend considering a device like the Symantec Firewall/VPN or Cisco PIX.  The Symantec device is inexpensive and easily supports up to 40 users or so.  It is web manageable and allows to redirect port traffic to specific internal devices...  It does some other stuff like DHCP too.

A quick look at CNET turned up "TCP Port Rerouter 1.0" which is described as allowing you to redirect traffic to a specific port to another host.

******************************************
Looking at Moxa's site turned up this:

Host Based Mode:
The DE-211/DE-311/311M driver uses TCP Port 950 as a data port and 966 as a command port.

RAW Connection and Ethernet Modem Mode:
There are no command ports for these operation modes. Both modes only use a configurable TCP data Port, which is set to 4001 by default.

Pair Connection Mode:
There is no command port in this operation mode. The only port is a TCP data port, which is set to 4001 by default (this port number is fixed).
*******************************************

...so with a capable router or port routing software you would route TCP ports 950&966 (in Host based mode) to 192.168.0.10

Author

Commented:
We can get a thing from Edimax that appears to be the same thing.  Presumably, if I install a hardware router I can ditch ZoneAlarm and Wingate and the dedicated Internet box?

I notice that the router comes in a 1-port and a 4-port version.  I presume I can use a 1 port version (which actually has 2 ports - a LAN and a WAN port) and I connect the WAN port to the wireless modem and the LAN port to my LAN's switch.

Author

Commented:
We can get a thing from Edimax that appears to be the same thing.  Presumably, if I install a hardware router I can ditch ZoneAlarm and Wingate and the dedicated Internet box?

I notice that the router comes in a 1-port and a 4-port version.  I presume I can use a 1 port version (which actually has 2 ports - a LAN and a WAN port) and I connect the WAN port to the wireless modem and the LAN port to my LAN's switch.
Director, Integrated Systems
Commented:
I glanced at the data sheet and it looks like the same essential feature set. The virtual server function provides the port routing you need for the nPort.

The 4 port version is handy if you have other internet servers that can more safely exist between your firewall and internet connection (DMZ) or if your office is small enough to only need a couple of client connections... I think you'll be happier with administering that rather than the pc router.
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