[SOLVED] Faster WinSock sendto()

Faster WinSock sendto()

I'm using Windows Server 2008, and my program is in C++. I'm using WinSock2 and sendto() in a while(true) loop to send my packets.

Code like so:

while(true)
{
    if(c == snd->max)
        c = snd->min;

    dest.sin_addr.S_un.S_addr = hosts[c];
    iphead->destaddr = hosts[c];

    sendto(s, castpacket, pktsz, 0, castdest, szsad);

    ++c;
}

I need to send as much data to as many IPs in my hosts std::vector as possible, as quickly as possible.

I'm currently running on an i7 930 server, and I can only achieve 350Mbps or so.

I currently split my program into 4 threads, all running the while loop with different servers assigned to each thread. Adding more threads or running more copies of the program results in lower throughput.

I have another program running listening for replies from the servers. I get the servers from a master list and add them to my array. The problem at the moment is that it takes too long to go through all of them, and I want to check them regularly.

How exactly can I optimize my program/loop/sending here?

Solution

I would recommend moving to asynchronous I/O to speed things up a bit here. The main problem with sending them one at a time is that you are unable to queue up the next packet while the TCP stack is processing the current one.

Alterntively, you can go for a thread pool approach: you fire a certain number of worker threads, and each one picks up a client from a FIFO and sends data to the client. When a thread is done with its client, it puts the client back in the FIFO and picks up a new one. You can fill up the pipeline - but not swamp it - by tuning the number of worker threads.