Full duplex on Windows

[zeeMonkeez]

In testing a project on a Windows machine I noticed that apparently concurrent read/write operations are not supported on Windows: while reading data, the writing thread seems to block.
I did come across this article describing the FILE_FLAG_OVERLAPPED flag to initiate overlapped operations. Not knowing much about the Windows Serial API I don't know whether this is still relevant.
I do use .setTimeout (0, 1, 0, 0, 0); to reduce the time outs, however I also then start to lose data...

[brooksbp]

I ran across the same situation, but was surprised when I measured it. This was with my own code which is similar to the code in this project but does not use a lock (it's single-threaded).

Numbers for a UART device in hardware loopback (assign TXD = RXD):

  // Note that even though the software appears to be half-duplex, e.g.                                                                 
  //                                                                                                                                    
  //   for (;;) {                                                                                                                       
  //     tty.Write(..);                                                                                                                 
  //     tty.Read(..);                                                                                                                  
  //   }                                                                                                                                
  //                                                                                                                                    
  // the measured data rate is closer to full-duplex (for larger buffers):                                                              
  //                                                                                                                                    
  //   9600 baud:                                                                                                                       
  //                                                                                                                                    
  //   buffer_size=1B duration=799819us  TX bps=500.113 RX bps=500.113                                                                  
  //   buffer_size=4B duration=799951us  TX bps=2000.12 RX bps=2000.12                                                                  
  //   buffer_size=16B duration=1599840us  TX bps=4000.4 RX bps=4000.4                                                                  
  //   buffer_size=64B duration=3999859us  TX bps=6400.23 RX bps=6400.23                                                                
  //   buffer_size=256B duration=13599317us  TX bps=7529.79 RX bps=7529.79                                                              
  //   buffer_size=1024B duration=53597703us  TX bps=7642.12 RX bps=7642.12                                                             
  //                                                                                                                                    
  //   112500 baud:                                                                                                                     
  //                                                                                                                                    
  //   buffer_size=1B duration=799891us  TX bps=500.068 RX bps=500.068                                                                  
  //   buffer_size=4B duration=799956us  TX bps=2000.11 RX bps=2000.11                                                                  
  //   buffer_size=16B duration=799953us  TX bps=8000.47 RX bps=8000.47                                                                 
  //   buffer_size=64B duration=799911us  TX bps=32003.6 RX bps=32003.6                                                                 
  //   buffer_size=256B duration=1599892us  TX bps=64004.3 RX bps=64004.3                                                               
  //   buffer_size=1024B duration=4799703us  TX bps=85338.6 RX bps=85338.6