/*
 * ISA 563, Spring 2011
 * Copyleft by Muhammad Abdulla
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>

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

extern int errno;

#define QLEN 20

/*
 * echo-server.c -- demonstrates server-side socket operations
 */

#define PORTNUM 2345 

int main ( int argc, char *argv[] )
{
   int n;
   int sock, conn;
   int val;
   struct sockaddr_in sin ;
   struct hostent *hen ;
   char buf[1024];

   struct sockaddr_in remote_addr ;
   socklen_t addr_len ;
   addr_len = sizeof ( remote_addr ) ;

   // create socket
   sock = socket ( AF_INET, SOCK_STREAM, 0 ) ;
   if ( sock < 0 ) {
      fprintf ( stderr, "Can't create socket: %s\n", strerror(errno) ) ;
      exit(1) ;
   }

   memset ( &sin, 0, sizeof(sin) ) ;
   sin.sin_family = AF_INET ;
   sin.sin_addr.s_addr = INADDR_ANY ;
   sin.sin_port = htons ( (short) PORTNUM ) ;

   // try to bind to port_num
   val = bind ( sock, (struct sockaddr *)&sin, sizeof(sin) ) ;
   if ( val < 0 ) {
      fprintf ( stderr, "Can't bind socket: %s\n", strerror(errno) ) ;
      exit(1) ;
   }

   // we have to listen for TCP sockets 
   val = listen ( sock, QLEN ) ;
   if ( val < 0 ) {
      fprintf ( stderr, "Can't listen on socket: %s\n", strerror(errno) ) ;
      exit(1) ;
   }

   for ( ; ; ) {
      conn = accept ( sock, (struct sockaddr *)&remote_addr, &addr_len ) ;

      if (conn == -1) { // accept error
         if (errno == EINTR) { // caused by an interrupt
            continue; // try again
         } else {
            fprintf(stderr, "%s", strerror(errno));
         }
      }

      while ( (n = read(conn, buf, sizeof(buf))) > 0 ) {
         write(conn, buf, n);
      }

      // done processing request
      close(conn);
   }
}