minimum time intervals between sent packets

[esolve]

I'm writing a tcp and udp program which sends a lot of packets successively. for example, each packets(including ip/tcp/udp header) is about 60 bytes, in a program, e.g., udp_sender, it sends 5 packets each time, like:

  for(i=0;i<5;i++){
     send(sockfd, data, data_len);
  }

now I have a shell script

for i in `seq 1 20000`;do
  ./udp_sender
   sleep interval
done

I tried several values for interval, for example 50 milliseconds
so there are 100 packets per second
and the number of bytes is around 7KB/sec
it is not a bit value
but the receiver can only receive a small part of the packets
why?
thanks

[Rubberman]

This is UDP? UDP has no guarantees of delivery or sequence of packets sent vs. packets received. TCP takes care of that for you, but UDP does not. You have to code the protocols to deal with out-of-order or missing packets yourself.