#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/poll.h>

inline int CheckErrOut( int retcode, const char *msg )
{
  if (retcode != -1)
    return 0;
  printf("%s: errno=%d - %s\n", msg, errno, strerror(errno));
  exit(1);
}

int main(int argc, char *argv[])
{
  const char          send_msg[] = "foo bar";
  int                 ret = 0;
  int                 fd = -1;
  struct pollfd       pfd;
  struct sockaddr_in  from, to;
  int                 port = 0;

  if (argc > 1  &&  sscanf(argv[1], " %d", &port)==1)
    ;
  else
    port = 12345;

  fd = socket(PF_INET,SOCK_DGRAM,IPPROTO_UDP);
  CheckErrOut(fd,"socket");

  memset(&from,0,sizeof(from));
  from.sin_family = AF_INET;
  from.sin_addr.s_addr = INADDR_ANY;
  from.sin_port = 0;
  ret = bind(fd,&from,sizeof(from));
  CheckErrOut(ret,"bind");

  memset(&to,0,sizeof(to));
  to.sin_family = AF_INET;
  to.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
  to.sin_port = htons(port);
  ret = sendto(fd,send_msg,sizeof(send_msg),0,&to,sizeof(to));
  CheckErrOut(ret,"sendto");
  
  memset(&pfd,0,sizeof(pfd));
  pfd.fd = fd;
  pfd.events = POLLIN;  
  ret = poll(&pfd,1,10000);
  CheckErrOut(ret,"poll");

  if (ret != 0) {
    char   recv_buf[100];
    int    addrlen;
    
    ret = recvfrom(fd,recv_buf,sizeof(recv_buf),0,&to,&addrlen);
    CheckErrOut(ret,"recvfrom");
    printf("received: %u bytes\n", ret);
  }
  else
    printf("poll - timeout\n");
 
  close(fd);
  return 0;
}