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VNC Windows CE: A Comparison with Other Remote Control Solutions



Learnings:I tried copying the vnc files to \windows\*.* and adding a startup shortcut into \windows\startup. But when the unit was removed from the mains and repowered the files disappeared (I think \windows is loaded from a fixed image wiping out any changes you make).


VNC is not perfect. It has a few flaws that keep it from being theend-all solution for remote access computing. For example, windows oftendoes not update all the way. VNC tries to optimize display updates to reducenetwork traffic, and sometimes misses an update. Network latency sometimescauses delays in showing the status of the screen or a mouse movement.Sounds are not propagated at all. And certainly, displaying live videowon't come across. There are settings in the control panel for VNC toenable it to make more aggressive updates of the screen at the expense ofhigher network traffic.




vnc windows ce



Note to self: When building VNC server for FreeBSD, it cannot detectthe operating system in the X windows imake configuration files. I put inan additional statement in Xvnc/config/imake/imake.c at line596 that says:


I have a VNC client (192.168.0.66) and a VNC server (192.168.0.10) in my network. On the client runs Windows CE 5.0 and on the server VxWorks. The problem is, that the respnse to a touch click on the client is in some cases delayed. The delay time is 500 ms to two seconds.For problem analysis, I made a capture with wireshark. In the capture you can see that the clients reports to the server several zero windows (packet 185, 202, 211, 220,...). With packet 239 start the first Retransmission, then follows many ZeroWindow and Out-of-Order packets. The problematic retransmission is the packet 297. It retransmit packet 240 after 500 ms.I am surprised that the server send the retransmission after 500 ms and not faster. Can I found an explanation for this reason in my capture?


The trace shows that the client is not offering higher windowsizes than 6 MSS. So to avoid the zero window conditions, you need to speed up your client application (VNC client) or increase the tcp receive buffer to a more appropriate value.


Let's look at frames 67/68. Notice that Frame 67 (ip.id==0xc927) arrives before frame 68 (ip.id==c926) so those packets are arriving out-of-order and #68 is NOT a retransmission as wireshark tells us.67 is a naked ACK acknowledging everything up to frame 66. The windowsize shrank to 20 bytes below the MSS of 1426 That does not impress the server and within 33 µs it keeps on sending its 5 full MSS segments + 1 smaller segment - all data that had been sitting on the send_queue.


Shows up as a mass storage device or other linux USB gadget (CDC Ethernet) using standard USB class drivers.There's also a copy of acrobat reader for windows and mac on the CD.And technically, since it IS open hardware, you can buy a windows CE license for $10 and flash that on it instead of linux. Hackable devices: one step forward, one step back Posted Sep 3, 2009 4:58 UTC (Thu) by khc (guest, #45209) [Link]


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