Tribulations with RDT (remote desktop connection)

AlfredoQuintero

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Hello:
Did a project some months ago for a customer. It is a Windows 10 application running on an industrial PC which is not connected to the Internet. This IPC is connected to two LANs, one on the PLC side and one connected to a laptop computer connected to an access point that lets me use TeamViewer to connect to the laptop, and then using RDP connection I can check my application. The access point device is inside the building and the signal is not too good, and in rainy days it seems to get even worse, refresh of screens become unbearably slow.

Recently the OS on the laptop had some patches installed and now I cannot see my application on the IPC. The RDP does get connected to the IPC but the screen is black, at least from here. Maybe from the control room it is visible. Going there is not easy due to the several hundred kilometers distance and COVID restrictions, as it is a candy factory, and also they do not have budget to get me there and I do not want to go there on our dime.

I tried several things, like changing resolution, enabling "turn-off UDP on client" in the group security policy. I also downloaded the new MS RDP from the MS app store but the behaviour is the same with the new one, I only see an orange screen.

Tried the FreeRDP client (which requires no installation), and this one gets connected to the IPC but only for about 5 seconds, then it crashes. There is an application called Royal TS which has a lite version. Tested it here and looks very good, but would need permission from the customer to install it, so before doing this wanted to know if anybody has endured something similar to what I described here.

One more thing, I had to do an additional change, which was to create an entry in the HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Terminal Server Client. I added the DisableClipboardRedirection (TRUE) because my application is an Excel macro that does a lot of copy+paste and sometimes the connection with the RDP would crash the macro. But after I did the change the RDP was working OK for a few days. So either the problem is some Windows patch, or the fact that the communication with the wireless access point is not good could be causing this problem? I ran out of ideas, thanks for reading.o_O
 
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Yeah, that is also my experience, if the bandwidth of the connection is very little, RDP can be totally useless.

As an alternative to RDP, I suggest a VNC server on the PC that is to be monitored or operated remotely.
VNC requires much less bandwidth than RDP, and if you have a really awful connection you can dial back for example the color palette so that it is useable even in extreme cases.
You possibly wont be able to drag and drop files between the PCs, but you get a file transfer utility, which is also more stable. The file transfer may hang, but wont crash the connection.
And, VNC can be used on diverse devices. Not only Windows.
 
yes, Jesper but the bandwith between the RPD client and the RPD server is OK, because it is through a local area network. The slow part is the TeamViewer portion. That is the strange thing. It seems to be a problem with the MS RDP applications.
 
So it is something like this:
[PLC] ----(LAN 1)---- [ IPC port 1 / IPC port 2 ] ----(LAN 2)---- [ laptop port 1 / laptop wifi ] ----(wifi)---- [Access point] ----(www)----
------------------------[ Applikation / RDP server ] ---------------- [RDP client / Teamviewer Host] ----------------------------------------------

Teamviewer is quite effective, but you can also dial down the graphics color palette or resolution if the connection is bad.
You suspect that the RDP connection affects the Teamviewer connection.
I dont see that there is a need for RDP. You can use VNC in its place. Every time that I have to use RDP it is just painful.
Or why not use Teamviewer directly on the IPC ? Does the IPC not have wifi ? A USB wifi dongle costs nothing.

edit: Maybe focus on the wifi connection that strugles on rainy days.
It sounds to me that you can fix the problem with a directional antenna.
 
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Not true James, I RDP into a server every business day, no one is in that building, I get into the server every day.

I also RDP onto my laptop from my desktop on my office LAN. As long as you have the credentials, no one needs to acknowledge the connection on the other end.
 
Hello Phil, I would not want at this point to try the VNC because my application is an Excel macro that uses a lot of copy and paste.
I may have to try it though if I cannot find a solution, and it seems the VNC viewer does have some options that can disable clipboard effects.
I am able to connect with a shareware called "Royal TS." It seems I must have some setting incorrect on the RDP client.
I am posting a summary of what I have. Maybe it rings a bell on somebody's head.
Maybe my solution will be to continue using the Royal TS shareware.

20220421_TS_Royal_RDP.jpg
 
Hello Phil, I would not want at this point to try the VNC because my application is an Excel macro that uses a lot of copy and paste.
I may have to try it though if I cannot find a solution, and it seems the VNC viewer does have some options that can disable clipboard effects.
So you have already tried VNC, and with VNC you also have some kind of problem ?
If so, exactly how do these problems manifest themselves ?
 
I would not want at this point to try the VNC because my application is an Excel macro that uses a lot of copy and paste.
You think that VNC will have some kind of issue with the macro (VBA ?) in the Excel application ? I thought that you came to this suspicion because you had already tried it out. I cannot see how there should be any connection between a VNC connection and a VBA macro running in an Excel file on the VNC client PC.
A VNC server is merely a 'video camera' that sends the screen content to the VNC client, and in return gets mouse and keyboard commands from the VNC client.

The issues you have shown with RDP is exactly the kind I hate about it. Also, bandwidth is a greater issue with RDP than it is with other solutions.
 
I may try VNC if it is possible to disable clipboar redirection, becausr my macro usrsa lot of cooy paste and the vnc client could cause macro error. in RDP ir is lisdibke to disable this
 
In RealVNC you can disable clipboard redirection.
Unchecking 'Accept clipboard changes from server' should do the trick.
spayK.png


I am pretty sure you can do the same with UltraVNC, but I do not know exactly which setting it is.

OT:
I have dabbled a little Excel with VBA, but I must say that I have not had to use the clipboard at all. My VBA code only manipulates cells in an existing sheet. Having to use the clipboard sounds unreliable. This must give some other problems on the local PC if some other application is being used.
 

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