Serial RS232 to Ethernet Conversion


Thread Starter


Dear sir,

I am having RS 232 output device which gives its output data to the RS 232 port of PC using hyper terminal.

Now I want to shift this PC from same place i.e., 5 meter distance from RS 232 device) to 100 meter away from that instrument.

How can I get the same data to 100 meter away as RS 232 only supports up to 15 meter distance?

Would a serial to Ethernet converter work and how?

What are the requirement of PC for the same to work? Is there any software configuration required?

Thanks in advance.
Hi Nailesh,
You may want to use RS-232 to RS-485 on the both end, RS-485 can be achieving 100 meters length as required. I recommend you to use Moxa :

I'm not sure if Ethernet with UTP Cat-5/6 can go that long, as per experience you should use fiber optic cable instead of UTP cable. Theoritically, UTP cat-5 can achieve 100 meters, but this is under ideal conditions. With industrial environment that full of noise and interference I'm not sure if 100 meters length ca be achieved.


James Ingraham

>How can I get the same data to 100 meter away as RS 232 only
>supports up to 15 meter distance?

There are at least two ways to do this. The most obvious would be an RS-232 extender, which usually converts to Cat 5 cabling but NOT Ethernet. There is no software requirement, and they are relatively inexpensive. Search google for "RS-232 Extender" and you'll get plenty of hits.

>Would a serial to Ethernet converter work and how?
>What are the requirement of PC for the same to work? Is
>there any software configuration required?

Yes, it would work. You will need to make sure that the converter / gateway will do what you want, i.e. resend raw serial data in both directions. There are dozens of options to choose from. In this case, you will have to install a virtual COM port driver on the PC; after that your software shouldn't know the difference between it and a regular serial port. Make sure you can install drivers, and make sure the gateway has drivers for the OS you're running.

-James Ingraham
Sage Automation, Inc.
RS-232 current loop

A current loop modem converts from RS-232 voltage to a current loop for the long haul and then back to RS-232 voltage at the other end.

I have used two different methods for extending RS232 communication, in a way it depends on what you have available.

I have used a RS232-to-USB converter which then went through a USB extender using CAT5 cable (similar to This was because the extended range was needed for a USB device when we decided to connect with the RS232 analyzer.

Currently, I use serial over Ethernet converters for analyzers that are not natively Ethernet capable. After creating a virtual COM port, I am able to connect from anywhere while on the company network. I have two different boxes that I use, a LES404A from BlackBox (newer 1-port version is and an NPort5150 from Moxa ( Both work quite well if there is an existing Ethernet connection nearby.

So it comes down to: Do you have an existing Ethernet connection nearby to tie into or does wire need to be run?
Try a NPort 5110 by Moxa. It converts Ethernet to RS232 and viceversa, so you can have an extended length serial port. You need two of these and a long Ethernet cable, you configure this mode through its internal setup webpage and voila! The kit includes power supply and din rail bracket. I hope this helps.

IMHO ... this could be an interesting small project using the RaspBerry PI SBC.
With the newest version of the RaspBerry you have the choice between a LAN or WLAN connection.

But if you have luck the conversion could already be done by a RaspBerry project ...

Best Regards

Armin Steinhoff

PS: from a hardware point of view it would be an overkill .. but it costs just 35 EURO :)
In a past job a few years ago we had quite a few rtu's on the old pots phone lines, which we polled at a blistering 2400 baud. These were scattered over a large geographic area, that encompassed many districts. To save money, we utilized virtual comports and Lantronix single port serial servers to interface to modems at the local district offices. This allowed us to poll devices many hundred miles away, without incurring long distance charges. It worked quite well. Nowaday's I use Lantronix and Grid Connects in plant enviroments to bring in data (mostly via modbus). Converting a lot of rs-232 and rs-485 data to the encapsulated ethernet.

Curt Wuollet

Since you aren't getting any more than serial speeds, you might find converting to RS485 to be beneficial There's generally less hardware
involved and 100 meters of decent cable is pretty reasonable. It's differential transmission so noise is seldom a problem. I've found it to be a "set it and forget it" type solution. You can even use USB for a PC with converters that cost only a few dollars and at 100 meters you should be able to do much higher data rates than RS232 at any appreciable distance. I routinely get 38.4 kbaud at that sort of distance. It's been doing this for a long, long time with very little fuss. If the only way from point to point was an ethernet network then converters might make sense, but there are a lot easier and cheaper ways for a serial speed link. The 232 extenders can work but they are generally proprietary and not interoperable. RS485 hardware is universal.

First off, the distance limitation published for RS-232 (EIA-232) is one of capacitance, and is set at 2500 pF. Since most early cable had a 50 pF capacitance per foot, that set a limit of 50 feet. Now most cable runs around 12 pF per foot, so the capacitive limit would be a bit over 800 feet. Of course, reliable transmission will depend on baud rate as well as ground potential differences, so most still don't push past the 50 foot limit.........and achieving 800 feet is often problematic (mostly due to ground potential differences).

That said, if you are routing this between buildings, and especially if you have any issue with lightning in the area, I'd recommend you convert to fiber. Doing so will allow you to remain with RS-232 on both ends if you wish. Running copper is the cheapest solution and posts by others delineate all the options.