#include <sys/types.h>
#include <sys/fcntl.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>

#define SERVER_PORT 12345		/* arbitrary, but client and server must agree */
#define BUF_SIZE 4096			/* block transfer size */
#define QUEUE_SIZE 10

int main(int argc, char *argv[])
{	
  int s, b, l, fd, sa, bytes, on = 1;
  char buf[BUF_SIZE];			/* buffer for outgoing file */
  struct sockaddr_in channel;		/* hold's IP address */

  /* Build address structure to bind to socket. */
  memset(&channel, 0, sizeof(channel));	/* zero channel */
  channel.sin_family = AF_INET;
  channel.sin_addr.s_addr = htonl(INADDR_ANY);
  channel.sin_port = htons(SERVER_PORT);

  /* Passive open. Wait for connection. */
  s = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP); /* create socket */
  if (s < 0) fatal("socket failed");
  setsockopt(s, SOL_SOCKET, SO_REUSEADDR, (char *) &on, sizeof(on));

  b = bind(s, (struct sockaddr *) &channel, sizeof(channel));
  if (b < 0) fatal("bind failed");

  l = listen(s, QUEUE_SIZE);		/* specify queue size */
  if (l < 0) fatal("listen failed");

  /* Socket is now set up and bound. Wait for connection and process it. */
  while (1) {
        sa = accept(s, 0, 0);		/* block for connection request */
        if (sa < 0) fatal("accept failed");

        read(sa, buf, BUF_SIZE);	/* read file name from socket */

        /* Get and return the file. */
        fd = open(buf, O_RDONLY);	/* open the file to be sent back */
        if (fd < 0) fatal("open failed");

        while (1) {
                bytes = read(fd, buf, BUF_SIZE); /* read from file */
                if (bytes <= 0) break;		 /* check for end of file */
                write(sa, buf, bytes);		 /* write bytes to socket */
        }
        close(fd);				 /* close file */
        close(sa);				 /* close connection */
  }
}

fatal(char *string)
{
  printf("%s", string);
  exit(1);
}