Get latency from host in C++

Question

Using C++, I would like to use a command/class to get the latency time from pinging a host to use in my program. I tried using the ping command but there was no easy way to gather the time since its included with other statistical information. I was hoping for an easier approach.

Answer 1

The ping tool is usually implemented in C and works by sending ICMP Echo request packets over a raw socket,. The system time is recorded -- usually with gettimeofday on under posix -- when the Echo request is made and again when an Echo reply (if any) is received to determine the round-trip time. You can put the same functionality in your C++ application using sockets.

Otherwise, extracting the information from a ping system call is probably easier than you think. The key is to open a pipe to allow reading of the standard output of the ping command (see popen or _popen). A regular expression (e.g. "time=([0-9]*)") could be used to pluck out the desired data. If you don't have a regex library available, then extracting this data only requires fairly trivial string manipulation. The STL string class provides several algorithms that may be of use.

Answer 2

if you don't like regexes you can always loop through the output, looking for t followed by i followed by m followed by e followed by = by just stepping through the output string one piece at a time. store the pointer to the char after =, then step through futher and replace the next space by a zero. you now have a string with the latency, converting to a number can be done with the existing conversion functions.

e.g. if the output is in char* output with length stored in unsigned int length and the matched string needs to go in char* match...

for(unsigned int i = 4; i < length; ++i)
{
  if(output[i] == '=')
  {
    if((output[i-4] = 't') && (output[i-3] = 'i') && (output[i-2] = 'm') && (output[i-1] = 'e'))
    {
      match = &(output[i+1]);
      while(output[i] != ' ') ++i;
      output[i] = 0;
      break;
    }
  }
}

regexes are nicer though... they make your code look a lot a tider and readable. although if you don't have a library for them it will be faster to just implement it like this... :)

Answer 3

I understand this but the return value from a ping command is either 0 or 1. Is there an easier way than rediecting the standard output to a flatfile?