Problem with Serial ports when transfer exceeds 256 bytes

[raccoonone]

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.

[frank]

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

[raccoonone]

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?

[raccoonone]

This is still a problem in 3.0.10

[frank]

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?

[raccoonone]

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.

[raccoonone]

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

[replykate]

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.

[TKreuzer]

See also ticket #1548

[frank]

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