For small installations a simple workaround is to change the client's com port numbers in order to avoid conflicts. (This limitation only applies to rdp sessions TO Windows XP.) Tags: local resources, map com in rdp, redirect hardware, serial port mapping. Terminal server serial com port redirection and usbto serial adapter. Using remote desktop rdp to access serially connect computers saleseng august 16, 2018.
I have a client with 4 XP SP3 thin clients (HP t5740) that act as shipping stations. They have a scale hooked up to the serial port used to weigh packages. They RDP to a 2008 r2 server (with all the updates). Now, 2 of these thin clients are on the lan, and work just fine. The other two come across a wan/vpn connection and the only thing that doesnt work is the serial port redirection.
The funny thing is that they (the wan and lan tc's) worked when they connected to a 2003 TS box (which we have not been able to decom. Because of this). All 4 thin clients are identical, have the latest firmware, etc etc. The connection is a 10mbps down/2mbps up and we're using the same username to test all of them. The only difference is the wan. Is there some sort of latency requirement for serial port redirection or anything else causing this, usually in the past with issues like this it either works or it doesn't. I've not had some working and some not working like this.
Thanks for any help! Hi, Thank you for posting here. This is possibly a known issue due to application design and the redirected serial device.
![Serial Serial](https://www.fabulatech.com/img/products/spr/spr-scr.gif)
In detail, each WriteFile request on the virtual RDP serial port on the server will result in an RDP packet sent to the client; while each ReadFile request on the server will result in 2 RDP packets. As the result, if the application reads or writes 1 byte at a time by design, so each byte transferred will create one or two RDP packets. This is the underlying cause that serial communications to be significantly slower. As the issue is only occurring in WAN environment,i suspect whether it is a network issue.And the only difference is the wan. Regards, Clarence Forum Support Please remember to mark the replies as answers if they help and unmark them if they provide no help.
If you have feedback for TechNet Subscriber Support,. Please remember to click “Mark as Answer” on the post that helps you, and to click “Unmark as Answer” if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread. Thanks for thre reply, I wish it was better news!
How is it possible that on the wan clients remote desktop works, printer redirection works, everything except the serial port redirection works? It all worked with 2003 server, I find it hard to believe we're taking a step back with 2008r2 rdp unless some sort of change was made to this feature in the newer rdp clients. The network is not dropping any packets, and the latency is under 90ms. Do you have any documentation or links to show this is a known issue? I am in no way a RDS expert, so don't let this side track you if totally off base, but to me I would suspect the WAN or in this case the VPN. I am assuming you have some encryption as well as possibly a firewall on the VPN connection. Again, I don't know the communication process of RDP, especially on the serial port re-direction (who initiates the communications on that port, what ports and what protocol are being used, or even if it is any different then the user session) but it might be interesting if you have no other leads to look at monitoring the packets over that WAN/VPN; Either for blocked ports, blocked protocol+ports, or latency on the encryption/decryption of the packets causing issues.
![Port Port](/uploads/1/2/5/4/125466382/869830082.png)
Is everything over TCP or is UDP used in the redirection? Same ports as user session? Who opens the connection the client like in the user session or the server for the re-direction and is your firewall ok with this? Thanks for your proposed answer - I am having pretty much the same problem, and I tried this solution, but it did not improve the serial com port communication. Here is my scenario: I am trying to use a signature capture pin pad for my point of sale software. The pin pad driver creates a virtual COM port.
When communicating with the local computer directly, it works absolutely fine - communication is very quick. When I do an RDP session to a local server and share the COM port, there is also no problem - communication is very quick. However, once I try to reach a remote server and share the COM port, the communication is terribly slow and more often than not, the POS software ends up timing out. I have tried using an RDP session to the remote server over the WAN IP address of the server and using a VPN connection to it's local IP address, but both produce the same slow results. I'm using a Windows 7 (also tested with Windows XP) client connecting to Server 2008 R2 Server with remote desktop services. I made sure that all windows updates are installed to latest version. I also checked with the hardware manufacturer of the pin pad and I have the latest device drivers.
I also tried using a different serial pin pad (not using virtual com port drivers) but had the same result, so I don't believe it's a driver issue. I've seen that slow COM port redirection seems to be a fairly common issue, but I don't see any clear resolutions. Any help you can provide would be great!
I have a business that has a small branch office about 20 miles from it's HQ. They have a VPN (router to router) to connect the two, but due to the latency between the two, in order to make the application they use run (AVIMark veterinary software) we use Remote Desktop. That works great with one hiccup. They have lab equipment in the branch office that needs to send results to the software. I can use putty within the remote desktop and connect to the com ports assigned on the local machine they are using.
The data is getting through the RD session from the local machine the lab equipment is connected to. However the AVImark software looks for actual com ports on the computer it's running on (in this case the RD session). Since RD isn't actually creating a com port which can be seen in device manager it isn't working. Long story short. Is there any way to make the com ports from the local/host machine actually show up in a remote desktop session? (Serial ports is checked in the RD options, but that doesn't actually create the ports in device manager).
VS - Thanks for those links, I'll check them out. MD0221 - Yeah, that's the 'work around' but it takes about 45 minutes to load. AVImark as you know is an outdated software but also what almost everyone uses (although that is changing). VS - They do have a client server connection but it still has to pull everything over the network.
The way the software works is you create a shortcut to the exe file on the desktop and run it from there. So instead of it just sending data over the network it has to run the whole program over the network.
Justin, That's intriguing. Can you only re-direct one user/computer (RDS Session) to Server 2012 or is it an all or nothing? Zacharryw - I'd love to see what your using. CCWTech wrote: Justin1250 wrote: That PS command turns on com port redirection globally on the server. I believe it is disabled by default in 2012 So each session would be re-directed but would be session specific, am I understanding that correctly?
Don't quote me on this but if I remember correctly they are redirected by name and are globally accessible. So each port on each computer would have to have a unique number associated with it. But it is easy to change to change the COM port number in device manager. Go into the properties of the COM port.
Then under port settings hit advanced. You should be able to change the com port number here. Edited Jun 9, 2015 at 18:12 UTC. Old thread but if it helps someone searching for a solution, as this took me a while to figure out. RDP ports, redirecting local serial / com ports into a remote RDP session, does work. However, in Windows 10 at least, you have to set 'Do not allow COM port redirection' to disabled in local / group policy (gpedit) see image below. Once the policy has been changed and updated (gpupdate /force) or a reboot you are good to go.
Note1: Remote end com ports are rendered useless within the RDP session when Ports is checked when you connect. Note2: Nothing will change, at either end, in device manager. To see com ports available in the RDP session type mode into a command prompt within the RDP session. If you set Ports when connecting then the local com ports will be shown, if not you see the remote box com ports.
Computer Configuration Administrative Templates Windows Components Remote Desktop Services Remote Desktop Session Host Device and Resource Redirection.