Serial Servers over Ethernet – Virtual COM port mapping

Serial over Ethernet?

This article is going to go into the world of old school and obscure. That before we had the internet. Before we even had such a thing as RJ-45 jack to network with. There was only two cost effective ways of transferring data from one device to another during the 80’s and most of the 90’s. Parallel and Serial transfers. This allowed for computers to make a very primitive ‘network’ of sorts by pairing multiple serial connectors together to effectively talk to a program such as a BBS (Bulletin Board Systems).

With the introduction of USB the need for these types of adapters is greatly reduced over the years. The requirement of a serial port still arises from time to time whenever you are doing with older CNC Machinery, Thermal Printers, Solar power monitoring stations, Industrial PLCs, and most importantly to us hooking up to old machines like Commodores and Amigas to do file transfers. Maybe you want to hook your high speed network up to a 56k modem so you can re-live the days of dial-up?

It seems a little masochistic to us but there are people who really dig the whole “Nostalgia” theme. There you go! In this day and age where you can convert anything to anything there surely must be an effective means of virtualization serial over Ethernet right?

Let’s find out!

Video mirrors:

In case you have no-script enabled or for some reason cannot see the title video on this website. I have provided direct links for these videos.

  • WebM – Link – This is the newest video standard, works great on Opera, Firefox, Chrome, and newer android phones, not good for Safari, IE, Apple.
  • MP4 – Link – The most compatible codec but also rather large in file size. Make take a while to download.
  • OGV – Link – the fallback codec for older PC’s and Linux USB stick OS’s. 1st generation web video streaming based on Ogg-Vorbis encoding.

Our test subjects.

  We went over to the I.O.T. Workshop which then resolves to which sells different types of serial solutions for industrial environments. They also had an Ebay shop to where we bought ours from. This took almost a month for us to get because there was some confusion about the stock of the DTU-H100. Even though there’s been YouTube videos showing off the DTU-H100 it’s apparently being phased out of stock and the replacement will be the adapter below which is the HF2211.  After telling hi-flying that we’ll take the new model we got the units in about a weeks time.


Basic Frequency380MHz
Operating SystemeCOS
Interface StandardRJ45
Protection2KV electromagnetism isolation, shell insulation blocking
Network ProtocolIP?TCP?UDP?DHCP?DNS?HTTP?ARP?ICMP?Web socket?Httpd client
Security ProtocolClient ?SSL v3?2048bit? Encryption?AES-CCMP?3DES Authentication?SHA-1?MD5?Base-64
Standard802.11 b/g/n, Frequency : 2.412GHz ~ 2.484GHz
Network ModeSTA/AP/STA+AP
Access Terminal Quantity in AP ModeMax. 32 STA
Transmit Power802.11b: + 20 dBm (Max), 802.11g: +18dBm (Max), 802.11n: +15 dBm (Max), E.I.R.P. : <100 mW (include 3dBi antenna)
Receive Sensitivity802.11b: -89 dBm (@11Mbps, CCK) 802.11g: -81dBm (@54Mbps, OFDM) 802.11n: -71dBm (@HT20, MCS7)
Wi-Fi SecurityEncryption?TKIP?WEP?64/128bit??WPA?WPA2?AES-CCMP Authentication?PSK
Antenna InterfaceSMA(female)?50Ohm
Port Number2 (RS232+RS485)
Interface StandardRS-232?DB9 pin type? RS-485?2 wire?A+?B-?
Data Bits5?6?7?8
Stop Bit1?2
Check BitNone?Even?Odd?Space?Mark
Baud RateRS-232?600 bps~230.4K bps? RS-485?600 bps ~ 230.4K bps
Flow ControlRTS/CTS
ConfigurationBuilt-in webpage?Http Computer set-up software Serial command? CLI Support configuration record?Log Remote Configuration?Telnet
Virtual SerialWindows, XP/Vista, 7? Server 2003/2008
Size84 x 84 x 25?mm?
Input VoltageDC 5~18V
Working Current~220mA
Warranty1 year
In the DTU-H100 box you get everything you seen pictured above:

  • 5vdc 1amp power supply
  • DB9 Female – DB9 Female cord allowing you to hook up to a serial port of a PC.
  • RJ45 Cat5e cable for hooking it to your wired network.
  • 3db wireless antenna for hooking to a wireless network.

  This device we paid approximately $37(USD) on via Ebay direct from the Hi-Flying reseller.  


Basic Frequency320MHz
Operating SystemeCos
Interface Standard1 RJ45
Protection8KV Isolation
Network ProtocolIP?TCP?UDP?DHCP?DNS?HTTP Server/Client?ARP, BOOTP, AutoIP, ICMP?Web socket, Telnet, FTP,TFTP, uPNP, NTP, SNMP,Modbus TCP
Security ProtocolSSL v3 AES 128Bit DES3
Standard802.11 b/g/n
Network ModeSTA/AP/STA+AP
Access Terminal Quantity in AP ModeMax 32
Transmit Power802.11b: +20dBm(Max.) 802.11g: +18dBm(Max.) 802.11n: +15dBm(Max.)
Receive Sensitivity802.11b: -89dBm 802.11g: -81dBm 802.11n: -71dBm
Wi-Fi SecurityWEP64/WEP128/TKIP/ AES
Antenna Interface3dBi antenna
Port Number1RS232/RS485/RS422
Interface StandardRS232: DB9 RS485/RS422: 5.08mm connector
Data Bits8
Stop Bit1,2
Check BitNone?Even?Odd
Baud RateTTL: 300 bps~230400bps
Flow ControlNo Flow control Hardware RTS/CTS?DSR/DTR Software Xon/ Xoffflow control
ConfigurationWeb CLI XML import Telnet IOTManagerPC Software
Virtual SerialWindows, XP/Vista, 7? Server 2003/2008
Size95mm x 65mm x 25mm
Input Voltage5~36VDC or 9~50VDC
Working Current~200mA
Warranty1 year
Accessory1* Power Adapter 1* Serial Cable 1* Ethernet Cable 1* WiFi Antenna
The HF2211 is going to be a very similar list of hardware goods:

  • 5vdc 1amp power supply
  • DB9 Female – DB9 Female cord allowing you to hook up to a serial port of a PC.
  • RJ45 Cat5e cable for hooking it to your wired network.
  • 3db wireless antenna for hooking to a wireless network.

This device we paid approximately $42(USD) on via Ebay direct from the Hi-Flying reseller.  

Addressing the Raspberry Pi in the room.

While we may do another article about how to make a Raspberry Pi do exactly what these units are doing. The question has to be addressed:

Why would you even buy these things S? The Raspberry Pi can do Sooooo much more!

To which we agree with you! But a lot of customers are looking for a plug and play style hardware solution. When you start looking at the prices of these units where the maximum being $42 dollars. After you get your FTDI USB cable, your case, the Raspberry Pi itself. Not to mention the time for configuration. The cost savings just does not add up. It all comes to down the two questions you should be asking about any piece of technology:

What does it do?


How well does it do it?

To which we will be diving into that next.

The web interfaces.

Lets start off with the first Ethernet to Serial adapter. the DTU-H100


DTU-H100 Ethernet to Serial adapter.

First up is the older DTU-H100 Serial to Ethernet adapter. It’s web interface is rather basic and right off of the bat there’s some things that it should not do such as show your Wi-Fi Password in plain text the moment you login. That’s a little obnoxious. But never the less everything is here for you to change the baud rate of the serial port. Change the TCP Port of the adapter. And allowing us to switch between Access Point Wi-Fi modes and Standard Modes for hooking up to a prexisting network which is fantastic.

There is one neat feature on the DTU-H100 which did not exist on the HF2211 which is underneath the advanced tab you could do port mapping. Meaning that if you are hooked to a wi-fi router on one network. and that network wants to access something on the physical RJ-45 port. It can do that without having to link both networks to the WAN. This is handy if you have as PLC actually does have a web site and you want to see if your changes via serial are affecting it. You could map port 80 to for your PLC’s website as an example and it would work.    

HF2211 Ethernet to Serial adapter.

The first thing that we liked when we logged into the HF2211 is its status page. As in, it actually tells us what the Wi-Fi Connection is doing versus just throwing in our SSID and password crossing our fingers and hoping for the best.   Inside of the HF2211 system settings we actually ran into some problems. You see, when we first got our adapter from Hi-Flying for some reason the Ethernew Port Mode was switched to “WAN” instead of “LAN”. This meant that when we plugged in our RJ-45 cable from our laptop into this unit it did nothing. It responded to nothing on the 10.10.100.x IP addressing. The only way we were able to get into this unit is through the open AP mode during initial boot up and change it to LAN Ethernet Port mode and enable the DHCP. Then and only then did it start to behave like the DTU-H100. This is problematic because what if I changed the Wireless from Access Point mode to Standard Mode and misconfigured my SSID or password? We would be completely locked out!  

Nothing too much of note on the Serial Port settings as all of the necessary options are there to change your Baud rates and settings for whatever device that you are hooking up to .

Custom settings was blank and lacking any port forwarding unlike the DTU-H100. But a nice thing in the OTHERS second is the fact that you can upgrade the firmware via the web page instead of relying on any utilities which is a good thing. Overall, the website on the HF2211 is way nicer and the Wi-Fi Connection is stable once connected to an office environment.

WPA2 Woes with the DTU-H100 = No more updates.

Unfortunately as of 3/10/2019 the DTU-H100 is a discontinued router and thus no more updates will be available for this little box. This is unfortunete because there’s a bug dealing with sustained serial connections over the WPA2 Wi-Fi where after a few seconds the Wi-Fi card simply shuts down. This does not happen in AP mode where you are controller the WPA or open connection. Just in WPA2 when connecting to a modern network the DTU-H100 is not a good fit. I suppose the good news is High-Flying did update it enough where the website actually works and thus there was no need to go into serial command mode and hammer a ton of AT+ commands like what we were seeing some of the Chinese YouTubers doing. So bonus points there. The bad news is the DTU-H100 and even the HD2211 adapters have no hard reset button on the outside of the box. You have to go inside and either bridge some wires and press a button inside if you want to factory default this device. That’s a serious engineering flaw because a user can easily mis-configure the network connectivity of these boxes loosing all connection both serial , Wi-Fi , and ethernet. Leaving the user to void the warranty to get their box back online.

The software.

Probably one of the most problematic issues with working with Ethernet to serial ports especially in a Windows environment is getting port virtualization to work properly. And boy did we try a lot of different pieces of software.

  • com0com – This software was super promising because it was open source it had a library for com2tcp . But we simply were not able to understand how to get com2tcp working within the com0com environment.
  • Advanced Virtual Com Port – This one looked promising. But their free version didn’t allow you to actually map a TCP port. Sorry guys, we’re not paying for software until you can show me that your software can do the job. Make it time limited to 15 seconds if you must but because we put any money down on a software you need to show me it works.
  • Serial port Re-Director – Same Story as Advanced Serial Port really. Except a more expensive license.

What about just going to Hi-Flyings website! DUH!!!

Oh we went there! Although there’s a lot of utilities for debugging over TCP/UDP connections once you navigate the Chinese only menus. There’s actually no mention of serial port virtualization in either their manual or the software that they provide on their own site.

Download the files.

Of course this article would really suck if I didn’t provide a solution to this software problem now wouldn’t it? After heavy digging we found some software which did work from another serial chip manufacturer which we’re not even sure is still around anymore. We have not only the software packed up in this archive but a TCP/UDP Debug utility and and finally the manuals in case you want to configure these boxes old school with AT+ commands. Simply click on the red download button to begin getting our 7-zipped archive.

TCP&UDP Debug tool.

The first application we are going to talk about is the TCP&UDP Debug tool. This is incredibly handy when diagnosing if your ports are not only open on your Ethernet to serial server adapter. But if you can transmit and receive data. While plugging another computer with a terminal running on the DB9 end of the serial server. We launch this program . Of course we’ll probably want to change our language to english unless of course you could read Chinese. Then we’re going to click the CreateConnection button and the Create Connection window will pop-up like pictured above. Select type for TCP. Select the destination IP for whatever you used to access your server servers website. In our case it was Select the port for the default setting of 8899 unless of course you changed that on the serial servers website as well. Finally, Select the LocalPort to Auto and click the create button.

Underneath the new client mode you just made click on that Connect button in the left-hand column of your client.

Once connected you should be able to type in a whole bunch of text in the window above and click the Send button to blast that across the TCP connection to the ethernet to serial server.

Moving over to your destination terminal. In our case we are using PuTTY hooked to a FTDI USB to Serial chip on COM4. Start typing and you should be able to type back into it and the data should appear on the receiving end. If you can do this then we have verified that your ethernet to serial server is working from a hardware standpoint. But we still haven’t truly mapped a COM port now have we? Lets fix that next!

AXMR2W Configuration Utility – Virtual com mapping.

Lets install and launch the AXMR2W Configuration Utility. Once the program is started click on Virtual Serial Port and click Add.

The AXMR2W Configuration utility will ask which virtual COM port you wish to map to. Select whatever COM2 that isn’t physically installed onto your PC and click OK to continue, In our case it was COM2.

It should give a report back stating that the AXMR2W Configuration utility added a virtual serial port successfully.

Also, if you check your device manager you will see that a new device has been added under your Ports (COM & LPT) catagory for ASIX Virtual Serial Port (COMX) indicating that the device has been injected into our OS.

We of course have to configure what our virtual port does now don’t we? Click on the setting button and then make sure the connection protocol is set for TCP . The mode is set for client. The remote host IP set for whatever our Serial servers website IP was set for. Finally, the remote host port set for default 8899 or whatever you set yours for. You check check Connect at Windows Start if your going to be using this a lot. But do not check the box to Enable VCOM! it will add a number “2” to every character you type in.

Finally press the OK button to save these settings.

Under the Network area we click the Connect button to bridge our virtual driver to our Ethernet serial server. It should show a status of connected. The moment you see this you should be ready to launch whatever program you would like to communicate via serial to. The most common problems that happen after this is not setting your baud rate right between serial server and the device you are connecting to. But overall it works out very well. In our video we even demonstrated connecting to a ancient Zebra Z4000 printer and printing a 90kb file across this device without issue.

03/13/2019 – Thanks Windows 10 



  It appears Windows 10 has come to the ‘rescue’ of its users by protecting them from themselves by simply stopping the software from working all together! 

If you tried to use AXMR2W on a later version of Windows 10. This is the wonderful screen that you will be greeted with. Now, you can simply move the application out of the C:\program files\ folder and onto the desktop to bypass this error. However, when you attempt to map a COM port then this is what happens.

Getting the kiss of death from a newer OS is not fun. Thankfully we did find a solution that works out really well.

Luckily, There’s another software out there called HW-VSP3 from the Hardware group. Which makes a virtual port mapping software that does work with windows 10. And for bonus points it even works in a VMWare environment as we attempted to use ESXI’s v6.7 manual serial port mapping only to be met with failure. Now why does this company give out such an awesome piece of software you may ask? Because they sell their own version of a serial server. And for those factories and people in the industry looking for a TCP<->Serial solution you should buy a server from these guys over the Chinese adapters we got from eBay. Support those who support your business.  

When you first download this program it won’t let you do anything until you login.

So press that login button. Password is admin.

Alright, now before we go map our virtual port we want to show you the settings tab as this is important if you wish to use this utility in day to day operations. You’ll probably want to check the box to Create VSP Port when HW VSP Start-up so that it always maps a port whenever you launch this program. From there you could add this program as a string value in your registry under 


Just place a value for the software into there so it’ll always launch the moment you login to your computer.

Now we can go back to the Virtual Serial Port tab and type in our IP address and port number. in our case it was and port 8899 just like the website said. And press that Create COM button to continue.

It should then grey out and the only thing it will say under the VSP status is Created. Short, sweet and to the point.

Just to verify you can go into device manager and you will see a ELTIMA Virtual Serial Port (COMx) under Ports (COM & LPT).   At this point you are ready to launch PuTTY or practically any windows application to forward your TCP ports to whatever serial server that you choose including the HF2211 that we are using in this blog. The only thing that this program cannot do is automatically detect our serial server that is on the network because of course it was not made by this company. Completely understandable!

But at least the virtual serial port driver for windows 10 is flawless. Coming from a Freeware piece of software that is absolutely amazing! So much so that I’m leaving all of their advertisements in the screenshots I’ve made. Seriously guys spend a little more money and buy their servers instead of the HF2211 that we got! You’ll thank me later.

Final thoughts.

 These adapters are really cool for those who need to have serial ports in inconvenient places around the home as well as the office. It’s a great solution versus throwing a laptop or desktop in a closet somewhere. and although we had some set backs with the DTU-H100 failing on a WPA2 environment the HF2211 is a rock solid adapter. Of course it’s not as much fun as diving into shell on a Raspberry Pi and piping tty connections all over the place and listening to TCP sockets to pipe the data around.

It gets the job done from a hardware perspective which legitimately it’s the only and best thing you could ask for. Are these serial servers worth their price versus purchasing a more expensive brand from say HW-VSP3’s portbox? It seems to us that what you save in money initially you end up loosing in time down the road finding software that actually works with it. If your business environment is predominantly linux anyways where you can port data to a TCP/UDP address with just a few command lines it’s not the end of the world. But in the Windows OS it turns into a complete nightmare when it comes to this and going with name-brand hardware companies may be a better way of going.

May server protect you.


Leave a Comment to the Void