/* server4_select.c server skeleton SJ */
/* gcc -o server4_select server4_select.c -lnsl -lsocket -lresolv */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/wait.h>

/* how many pending connections */
#define BACKLOG 3

/* size of the send/receive buffer */
#define MAXMSG 1000

/* official network end-of-line is CR LF */
#define EOL "\015\012"

/* this macro can be used to check errors, see client2.c to do without */
#define ERRORCHEK(var, value, command)  if (var == value) {     \
                                            perror(command);    \
                                            exit(1);            \
                                        }


int main(int argc, char *argv[])
{
  int ssock, csock;  			/* listen on ss, new connection on csock */
  struct sockaddr_in own_addr;	/* my address information */
  struct sockaddr_in c_addr;	/* client address information */
  unsigned int sin_size = sizeof(struct sockaddr_in);
  int status, numbytes;
  char rbuf[MAXMSG]; /* receive buffer */
  char sbuf[MAXMSG*2]; /* send buffer */
  char yes='1';
  fd_set fds, orig_fds;
  int fdmax, i;
  int port = 9876;      /* default port */

  printf("exit by pressing any key\n");

  /* port as optional parameter */
  if (argc > 1)
	  port = atoi(argv[1]);

  /* get socket */
  ssock = socket(AF_INET, SOCK_STREAM, 0);
  ERRORCHEK(ssock, -1, "socket");

  /* reuse port immediately */
  status = setsockopt(ssock, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(int));
  ERRORCHEK(status, -1, "setsockopt");

  /* fill in the own address */
  own_addr.sin_family = AF_INET;         
  own_addr.sin_port = htons(port);
  own_addr.sin_addr.s_addr = INADDR_ANY; /* automatically fill with own IP */
  memset(&(own_addr.sin_zero), '\0', 8);

  /* bind to port */
  status = bind(ssock, (struct sockaddr *)&own_addr, sin_size);
  ERRORCHEK(status, -1, "bind");

  /* listen the port */
  status = listen(ssock, BACKLOG);
  ERRORCHEK(status, -1, "listen");

  /* set up file descriptor set */
  FD_ZERO(&orig_fds);
  FD_SET(ssock, &orig_fds);
  FD_SET(STDIN_FILENO, &orig_fds); /* for keyboard */
  fdmax = ssock;

  while(1) {  /* main accept() loop */

	  /* copy to temporary fds, select() changes the set */
	  fds = orig_fds;

	  status = select(fdmax+1, &fds, NULL, NULL, NULL);
	  ERRORCHEK(status, -1, "select");

	  /* quit (cruely) on user input */
	  if (FD_ISSET(STDIN_FILENO, &fds)) {
		  close(ssock);
		  exit(0);
	  }

	  /* check for new connections */
	  if (FD_ISSET(ssock, &fds)) {
		  sin_size = sizeof(struct sockaddr_in);

		  /* accept the waiting new connection */
		  csock = accept(ssock, (struct sockaddr *)&c_addr, &sin_size);
		  if (csock == -1) {
			  perror("accept");
			  continue; /* do not exit even if a connection failed */
		  }

		  /* add to active fd set */
		  FD_SET(csock, &orig_fds);
		  if (csock > fdmax)
			  fdmax = csock;

		  printf("server: new client: %s\n", inet_ntoa(c_addr.sin_addr));
	  } /* if ssock */

	  /* iterate over other sockets to find which socket is ready for reading */
	  for (i = 0; i <= fdmax; i++) {
		  if (FD_ISSET(i, &fds) && (i != ssock)) {

			  numbytes=recv(i, rbuf, MAXMSG-1, 0);

			  if (numbytes > 0) {
				  /* succesfull recv */
				  /* terminate message to make a string */
				  rbuf[numbytes] = '\0';

				  printf("Message was \"%s\"\n", rbuf);

				  /* construct reply */
				  sprintf(sbuf, "You sent me \"%s\"%s", rbuf, EOL);

				  /* send reply */
				  numbytes = send(i, sbuf, strlen(sbuf), 0);
				  ERRORCHEK(numbytes, -1, "send");

				  if (numbytes != strlen(sbuf))
					  printf("Only %d bytes sent! Should have used repeated send...\n", numbytes);

			  } else {
				  /* closed pipe, or error */

				  if (numbytes == -1)
					  perror("recv");
				  close(i);
				  FD_CLR(i, &orig_fds);


			  } /* else */
		  } /* if ISSET */
	  } /* for i */

  } /* while(1) */

  close(ssock);

  exit(0);

} /* main() */