UDP server/client performance in C

[anya]

Hi,

I want to test the performance of server/client arhitecture that I wrote but I have problems with non-blocking sockets. When I use fcntl I can not run client and server to work at the same time. While I run server client has already sent 5000 replies back although the server is not start to stream. How
can I make difference on client when server isn't turned on and when packet is lost? In my code client
behaves same.
On the other side, when I don't use fcntl then If I client doesn't receive packet
it blocks and wait on that packet, he even don't sent a reply back. I want that
client send back reply and to continue to receiving packets.


I dont want to use sleep because I need real time performance.

I'm wondering how real application are working, what is trick to implement this?

Thx


server

    fcntl(socket,F_SETFL,O_NONBLOCK);

    while(1){

        sendto clients
        pthread_create(reply_processing)
  
    }

    reply_processing(){

        recvfrom_clients

   }

client

    fcntl(sd,F_SETFL,O_NONBLOCK);


    while(1){

        bytes = recvfrom server, buf

        if(nbytes != -1){

            if(buf > = 512) write
            else EOF return 1;
    


        }else{

            lost++
            nack sent

}
    }

[Salem]

Well that's how UDP is supposed to work.

If you want guarantees, then you need a TCP connection.

The best thing to do is to establish a TCP connection to establish connectivity, and provide a reliable means of communication between the client and server.
In parallel to that, you use UDP to stream volumes of data with minimal overhead, and build in a bit of tolerance for missing, duplicate, out-of-order packets.

[anya]

Well the problem is that I can not use TCP at all because broadcastin via TCP is not possible and that is excatly what I need, I broadcast stream to clients. Is there any way to control UDP, just this thing how to detect server activity as I explanied above?

[Salem]

Unless each client sends a periodic UDP message "I'm alive" and you hope enough messages get to the server for it to continue sending updates to the client.