I am trying to do communicate between VMs and ESX using emulated serial lines. The destination on the ESX machine is a socket and the source is an application writing directly to COM2. The communication is unreliable even though the transfer is all done on one physical machine. Data disappears from the pipe, most notably in ESX to VM communications (ESX to VM data is mostly okay, though some loss does occur). The higher the COM port speed, the more likely data is to be lost.

I would think that transfers done on one physical host should be deterministic. It appears they aren't.

Any idea why this is happening?