UDPWrite in a loop. "A Windows Sockets function call returned an unexpected error."

Question

Hello together,
i use UDP Support Library in NI CVI 9.0. When i wait for receiving a packet at the pc to send then a packet from the pc, the functions UDPRead and UDPWrite work fine. If i want to test the maximum throughput, i put the UDPWrite in a loop, but then an error occurs. It is "kUDP_UnexpectedWinsockError"
Error Popup:
"NON-FATAL RUN-TIME ERROR:   "main.c", line 53, col 22, thread id
0x00000C18:   Library function error (return value == -6822
[0xffffe55a]). A Windows Sockets function call returned an unexpected
error."
Line 53:
status = UDPWrite (channel, 60100, "192.168.1.10", pOutputBuffer, 1458);
the whole loop:
while(1)
status = UDPWrite (channel, 60100, "192.168.1.10", pOutputBuffer, 1458);
counter++;
if(counter>50)
break;
else{;}
The error occurs after 3-16 packets have been sent. If i step through the programm, no error occurs. So i guess its because the UDPWrite command is invoked too fast. pOutputBuffer has static data. I could use a delay in the loop, but then i dont know how to configure for maximal throughput.
Any ideas how to avoid this error?
Regards Florian

Answer 1

Hello and thank you for your answer. Sorry that i reply a month later.
I dont know what you mean by "let 'er rip approach". Do you mean something like:
status = UDPWrite (channel, 60100, "192.168.1.10", pOutputBuffer, 1458);
if(status==0)
 counter++;
else
  Delay(0.00005);
I did not yet try to put the packet number in the payload, but there is just a 30 cm crossover cable between the two devices, no switch, no router. So the sequence should not be interruptet. And even if they arrive in chaos, i dont mind.
I have contacted the NI support 2 weeks ago, but no response yet.
I did some tests with a delay between the execution of UDPWrite(). The code:
float time = 0.0;
 for(i = 1; i < 1000; i++)
  status = UDPWrite (channel, 60100, "192.168.1.10", pOutputBuffer, 1458);
  time = 1.0 / i;
  Delay(time);
The results:
For i between 1 and 1000: no error, the speed of the last ten packets was about 6.5 MBit/s
For i between 1000 and 2000: error occured at i = 1585 (variable time in Delay was 0.0006313), the speed of the last ten packets was about 8 MBit/s
Then i put some constant values in Delay and ran 100 UDPWrite iterations:
Delay(0.0006): 7.48 MBit/s
Delay(0.0001): 10.7 MBit/s
Delay(0.00001): error occured at i=31, speed of 31 packets was 12.0 MBit/s
Delay(0.00008): 100 of 100 packets, speed 10.9 MBit/s
Delay(0.00005): error at i=41, speed of 41 packets 11.1 MBit/s