Converting RS-232 to IP and back


Thread Starter


I have 4 (four) outstations with traffic dataloggers on them. All have an RS-232 communications port. An ethernet switch will be installed in the same cabinets as each of the dataloggers. In a control center, there is a PC running software for telemetry, that can talk only to the two comms ports on the PC. It is meant to work with modems. There is also an ethernet switch in the control center. If I put an RS-232 to IP converter near each datalogger (any recommendations?), giving an IP address to that equipment, what can I put in the control center? Is there any kind of "IP modem", either by software or hardware?
Please help!
A company called Comtrol has a product called a RocketPort Serial Hub that might solve your problem. You attach the Rocketport to the network and to you serial device. Software running on any other PC on the network allows the
serial device to look like a local com port. Note, I looked into this product for a project that has been cancelled, so I haven't actually used it. I've heard that it works well, though.

Glenn Wouters

Suggest checking out "": and take a look at their Cobox-Dr1. I have used it to send Rs 232 serial daqta over an Ethernet link. It works well. They also provide a serial port re-director to an IP address
National Instruments ( makes 2 and 4 port RS-232 to Ethernet converters.
Here are links for the products:


The driver software allows the serial ports to be mapped as additional Com Ports on your PC. Also, the software allows multiple computers to access the different ports simultaneously (note: only one computer can access any single port at a

Moxa at "": has a number of devices that will serve as an interface between your data logger and the switch. One end of a single port device will connect to your data logger, via a DB-9, the other side of the device connects to the network via an RJ45. The remote computer, assuming its a PC running windows, will have a driver installed that will make the data logger, now remote to the PC, appear as a local com port. Whatever software comunicates with the data logger will now use this com port and the network is basically transparent.

If you need any more info on this you can contact me at: "[email protected]", mailto:[email protected]

Erich Mertz
Actually, this is quite easy. We have a product which allows Hayes/AT type commends from an RS232 serial port to control a TCP/IP socket/session. I believe several of our competitors also supply similar products - but I'd get fired if I pointed them out directly (check the web for Digi, Atop, and others).

You'd just do the following:
1) put this device on your serial port
2) connect the RJ45 to your Ethernet switch
3) configure it to support a connection mode of "Modem Mode"
4) change the phone numbers in your application to IP addresses
5) When your application issues an "ATDT 192168002023,10000", our device opens a socket to remote IP TCP port 10,000. If the TCP port is always the same, you can remove this from the ATDT command and configure this into the device directly for use each time.
6) When the socket is active, your application will see the "CONNECT" response.

You'll find it works just as you expect with no changes to your PC telemetry application - there is a huge move in the pipeline/SCADA/remote building HVAC management to replace dial-up modems with TCP/IP connections and this feature is targeted directly at this application.

You can see a manual at " ": - page 4-8 table 4-6 shows the basic commands supported.

The latest release of the firmware also allows the device is "answer" sockets from the network, but this is explained only in the firmware
release notes at: "":


Lynn August Linse, Senior IA Application Engineer
15353 Barranca Parkway, Lantronix Inc, Irvine CA 92618
[email protected]
Tel: (949)300-6337 Fax: (949)453-7152
One solution:

Place an Opto 22 SNAP Ethernet I/O system at each datalogger location. (This is comprised of a rack, power supply, a "brain" or processor, and various I/O modules.) Place a serial I/O module on the rack and connect to the datalogger.
Connect the "brain" to the Ethernet switch with a Category 5 cable (Ethernet cable). If you'd like more information from the datalogger locations
(temperature, humidity, door status, dry contacts, etc.) simply place the additional I/O modules necessary on the rack next to the serial module.

Next, install Tactical Software's Serial/IP software on the PC (~$84). The softare will allow you to map the PC's COM ports to IP addresses. For example, you would map COM1 on the PC to the remote SNAP I/O system's IP address followed by a port number that is associated with location of the serial I/O module on the rack (for example:

You now have a "virtual" connection to your dataloggers. This, of course, is assuming you've established a physical or virtual connection between the Ethernet switches in the control room and the remote sites (over the Internet for example). I am basing that assumption on the fact you haven't asked about that connection.



Remember, if you decide to place more I/O modules on the rack to obtain additional information from the remote sites, the SNAP Ethernet I/O system is
capable of not only tunneling your serial datalogger information, but simultaneously providing the additional remote site data via many standard formats, including email, SNMP, or XML to a Web server. Think of it as a functional, low cost remote telemetry unit, in addition to a serial to IP converter.

Enough sales pitch. Good luck with your project.

Call with questions - 909-695-3003. Benson