/* UDP torture server - receives packets from client */
 
#include<stdio.h>
#include<stdlib.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<arpa/inet.h>
#include<unistd.h>
#include<netdb.h>
#include<fcntl.h>

#define SETLOCALINFO bind
#define SETPEERINFO connect

#define LISTENPORT 40000
#define BUFSIZE 128

int main(int argc, char** peer)  
{

  int sockfd, i, x, y,result, mlen;
  unsigned int plen;
  unsigned char buffer[BUFSIZE];
  struct sockaddr_in peeraddr;  // used by sendto
  struct sockaddr_in myaddr;    // used by recvfrom
  sockfd = socket(AF_INET,SOCK_DGRAM,0);
  myaddr.sin_family = AF_INET;
  myaddr.sin_addr.s_addr = htonl(INADDR_ANY); // accept from any source ip
  myaddr.sin_port = htons(LISTENPORT);
  plen = sizeof(peeraddr);  mlen = sizeof(myaddr);
  bind(sockfd,(struct sockaddr *)&myaddr,mlen);  // bind still needed.

  // Can't receive packets while other side is ready:
  printf("press a key to begin: "); getchar();
  // why not needed for TCP?  because of the 3-way handshake


  for(i=0;i<100000000;i++)
    {
      result = recvfrom(sockfd,buffer,BUFSIZE,0,(struct sockaddr*)&peeraddr,&plen);
      // extract and print sequence number inside first 4 bytes of buffer:
      x = *((int*)buffer);
      printf("packet %d received\n",x);

      // intensional delay to throttle server
      for(x=0;x<10000000;x++) { x++; x--; } 
      
    } // for i



  /* how do I know if other side closed connection?  YOU DON'T - THERE 
     IS NO "CONNECTION"! 
  */

  close(sockfd); // only have local meaning - no packets exchanged.
  exit(0);
}