How do I send UDP packets at a specified rate in C++ on Windows?

I'm writing a program that implements the RFC 2544 network test. As the part of the test, I must send UDP packets at a specified rate.

For example, I should send 64 byte packets at 1Gb/s. That means that I should send UDP packet every 0.5 microseconds. Pseudocode can look like "Sending UDP packets at a specified rate":

while (true) {
    some_sleep (0.5);
    Send_UDP();
}

But I'm afraid there is no some_sleep() function in Windows, and Linux too,开发者_如何学C that can give me 0.5 microseconds resolution.

Is it possible to do this task in C++, and if yes, what is the right way to do it?

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Two approaches:

• Implement your own sleep by busy-looping using a high-resolution timer such as windows QueryPerformanceCounter

• Allow slight variations in rate, insert Sleep(1) when you're enough ahead of the calculated rate. Use timeBeginPeriod to get 1ms resolution.

For both approaches, you can't rely on the sleeps being exact. You will need to keep totals counters and adjust the sleep period as you get ahead/behind.

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This might be helpful, but I doubt it's directly portable to anything but Windows. Implement a Continuously Updating, High-Resolution Time Provider for Windows by Johan Nilsson.

However, do keep in mind that for packets that small, the IP and UDP overhead is going to account for a large fraction of the actual on-the-wire data. This may be what you intended, or not. A very quick scan of RFC 2544 suggests that much larger packets are allowed; you may be better off going that route instead. Consistently delaying for as little as 0.5 microseconds between each Send_UDP() call is going to be difficult at best.

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To transmit 64-byte Ethernet frames at line rate, you actually want to send every 672 ns. I think the only way to do that is to get really friendly with the hardware. You'll be running up against bandwidth limitations with the PCI bus, etc. The system calls to send one packet will take significantly longer than 672 ns. A sleep function is the least of your worries.

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You guess you should be able to do it with Boost Asios timer function. I haven't tried it myself, but I guess that deadline_timer would take a boost::posix_time::nanosec as well as the boost::posix_time::second

Check out an example here

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Here's a native Windows implementation of nanosleep. If GPL is acceptable you can reuse the code, else you'll have to reimplement.