// Source code arr_serv.c
// Written by Darren Challey
// Rensselaer Polytechnic Institute
// Spring 2000

// This server is to be used to determine the smoothing characteristics
//   of traffic shapers.  It determines mean, min, max, and standard 
//   deviation of arrival times
// Based upon programs found in "UNIX Network Programming" - Stevens

#include <stdlib.h>
#include "netinet/in.h" // Needed for sockaddr_in struct
#include <sys/time.h>   // Needed for timeval
#include <stdio.h>      // Needed for file I/O
#include <errno.h>      // Needed for error function
#include "dc_const.h"   // Needed for program constants

int main()
{
  // Open a file to write data
  FILE *arrData; 

  int sockfd = 0;              // socket file descriptor
  int in = 0;                  // input received from socket
  int a = 0;
  char msg[MAXLINE];
  double arrive[LOOP + 1];
  double delta[LOOP + 1];
  double mean_sum = 0.0;
  double mean = 0.0;
  double std_sum = 0.0;
  double diff = 0.0;
  double std_dev = 0.0;
  double min = 10.0;
  double max = 0.0;
  int count = 0;
  int sec = 0;
  double mic = 0.0;
  struct sockaddr_in servaddr;
  struct sockaddr_in cliaddr;
  struct timeval tv;

  // Initialization
  for (a = 0; a < MAXLINE; a++) {
    msg[a] = ' ';
  }
  arrive[0] = 0; // Array element not used
  delta[0] = 0; // Array element not used


  printf("\nStarting Server\n");
  

  if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) { 
    perror("No Socket");
    printf("errno = %d.", errno); // p475
    exit(1);
  }

  // If socket is successful, sockfd will be a small positive integer 
  // arrData = fopen("/tmp/arrData.txt, "w+");
  arrData = fopen("arrData.txt", "w+"); 
  // w = write-enabled, + will allow file to be overwritten

  bzero(&servaddr, sizeof(servaddr));	   // set entire structure to 0's
  servaddr.sin_family      = AF_INET;      // set family to IPV4
  servaddr.sin_addr.s_addr = CLIENT_IP;    // set in dc_const.h
  servaddr.sin_port        = htons(52330); // randomly selected ephemeral
                                           // ports as being 49152 to 65535	
  if ( bind(sockfd, (struct sockaddr*) &servaddr, sizeof(servaddr)) < 0 )
    {    
      printf( "bind failed" );
      exit(1);
    }
  else printf("\nBind Successful\n");

  // Read information from the socket
  in = recvfrom(sockfd, msg, MAXLINE, 0, NULL, NULL);

  while(msg[0] != 'E') { // Loop until last datagram received

    count++;

    // Determine arrival time
    gettimeofday(&tv, NULL);
    sec = tv.tv_sec;
    mic = tv.tv_usec / 1000000.0;
    arrive[count] = (double)sec + mic;

    // Print arrival time to the screen and file
    printf("\ntime arrived: %f", arrive[count]);
    fprintf(arrData, "%f\n", arrive[count]);

    // Read information from the socket
    in = recvfrom(sockfd, msg, MAXLINE, 0, NULL, NULL);

  } // End of Loop while not last datagram


  // OUTPUT OF RESULTS ////////////////////////////////////////

  printf("\n\nTotal Packets Rec'd = %d", count);

  // Calculate the mean time of arrivals
  for (a = 2; a < LOOP + 1; a++) {
    delta[a] = arrive[a] - arrive[a - 1];
    mean_sum += delta[a];
    if (delta[a] > max) max = delta[a];
    if (delta[a] < min) min = delta[a];
  }
  
  mean = mean_sum / ((double)LOOP - 1.0);
  printf("\nMean interarrival time = %f", mean);

  // Calculate Standard Deviation
  for (a = 2; a < LOOP + 1; a++) {
    diff = mean - delta[a];
    std_sum += diff * diff;
  }
  
  std_dev = std_sum / ((double)LOOP - 1.0);
  printf("\nMinimum interarrival time = %f", min);
  printf("\nMaximum interarrival time = %f", max);
  printf("\nStandard Deviation = %E", std_dev);

  fclose(arrData);
  printf("\n\n");

} // End Main