Opened 15 years ago

Closed 14 years ago

#5135 closed defect (duplicate)

Problem with Serial ports when transfer exceeds 256 bytes

Reported by: raccoonone Owned by:
Component: other Version: VirtualBox 3.0.8
Keywords: serial Cc:
Guest type: Linux Host type: Windows


When passing through a connection to a serial device VirtualBox doesn't send the data correctly. If the device sends more than 256bytes of data at a time VirtualBox seems to buffer it into 256byte piece, and only sends a piece when there is a communication from the OS to the device. I'm running VirtualBox on a Windows XP host, with an Ubuntu Guest.

Change History (9)

comment:1 by Frank Mehnert, 15 years ago

How is the serial port connected to the host (VM settings)?

in reply to:  1 comment:2 by raccoonone, 15 years ago

Replying to frank:

How is the serial port connected to the host (VM settings)?

I have it configured as: Port Number: COM8 Port Mode: Host Device

Anything else you need to know?

comment:3 by raccoonone, 14 years ago

This is still a problem in 3.0.10

comment:4 by Frank Mehnert, 14 years ago

Well, there is indeed buffering in the host part of the serial device implementation. The send buffer is 128 bytes long but as far as I can see, as soon as one byte arrives it is forwarded to the host's serial interface. But it can happen that the guest is sending too fast: If the buffer overruns, bytes will be dropped. Do you experience data loss or just bursts?

comment:5 by raccoonone, 14 years ago

Bursts. It will send all of the data from the device to the guest, if I keep "pinging" the device by sending some data from the guest to the device.

comment:6 by raccoonone, 14 years ago

This is still a problem in 3.0.12, do you need an additional information to debug this?

comment:7 by e, 14 years ago

I have the same problem. (sorry for my bad english I am french ). I tried to send a array (trame) from a windows xp host to a ubuntu (in VM). Only 258 bytes were send. If I try to send more, all my array is corrupted.

I tried to slow down transfert but no changement.

OS Host: WINDOWS XP SP3. OS Guest: Ubuntu 9.10. guest addon installed.

speed: 9600 bauds.

comment:8 by Timo Kreuzer, 14 years ago

See also ticket #1548

comment:9 by Frank Mehnert, 14 years ago

Resolution: duplicate
Status: newclosed

Let's close this as a duplicate. VBox 3.2.4 should definitely improve the situation.

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