/*
   tcp1-serv.c: illustrates an parallel TCP server
*/

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

int main(int argc, char *argv[])
{
   int s1;			/* s1 = listen socket */
   int s2;			/* s2 = connect socket */
   struct sockaddr_in me;	/* My own Internet address */
   struct sockaddr_in myname;	/* Used to retrieve my TCP port */
   int    myname_len;

   struct sockaddr_in from;	/* Internet address from client */
   int len; 			/* length associated with `from' */

   char c;			/* Used to get data from connection */

   if (argc == 1)
    { printf("Usage: %s port\n", argv[0]);
      exit(1);
    }

   /* ---
      Create a socket
      --- */
   s1 = socket(AF_INET, SOCK_STREAM, 0);

   /* ---
      Set up my own Internet address to bind to the socket
      --- */
   me.sin_family = AF_INET;			/* Put in the family */
   me.sin_port = htons(atoi(argv[1]));		/* Put in the port number */
   me.sin_addr.s_addr = htonl(INADDR_ANY);	/* Use wildcard address */

   /* ---
      Here goes the binding...
      --- */
   if (bind(s1, (struct sockaddr *) &me, sizeof(me) ) < 0)
    { perror("bind:");
      exit(1);
    }

   /* ---
      Just for curiousity sake, let's find out the name of the socket...
      --- */
   myname_len = sizeof(myname);
   if (getsockname(s1, (struct sockaddr *) &myname, &myname_len) == -1)
    { printf("Trouble: system did not find my socket...\n");
      exit(1);
    }
   printf("Server's listen socket is binded to:\n");
   printf("  myname.sin_family = %u (should be AF_INET = %u)\n",
		myname.sin_family, AF_INET);
   printf("  myname.sin_addr.s_addr = %u\n", myname.sin_addr.s_addr);
   printf("  myname.sin_port = %u\n", myname.sin_port);



   /* ---
      Specify the maximum number of `backlogged' connection requests
      --- */
   listen(s1, 5);

   /* ---
      After making our socket public, the server wait for connection requests
      --- */
   while (1)
    {
      /* ---
         Wait (i.e., block) until someone makes a connect call to my s1 socket
	
	 NOTE: accept RETURNS a socket descriptor similar to the socket() call
	       BUT a huge difference is accept aslo did a bind to it without
	       asking your permission
	 --- */
      printf("Ready to accept a new call.....\n");

      len = sizeof(from);
      if ( (s2 = accept(s1, (struct sockaddr *) &from, &len)) < 0)
       { perror("accept: ");
         exit(1);
       }
      printf("\n\nNew call accepted.....\n\n");
      printf("**** Information about this call:\n");

      /* ---------------------------------------
	 Print info of the listen socket
	 --------------------------------------- */
      myname_len = sizeof(myname);
      getsockname(s1, (struct sockaddr *) &myname, &myname_len);
      printf("The listen socket is:\n");
      printf("  sin_addr.s_addr = %u\n", myname.sin_addr.s_addr);
      printf("  sin_port        = %u\n\n", myname.sin_port);

      /* ---------------------------------------
	 Print info of the data socket
	 --------------------------------------- */
      myname_len = sizeof(myname);
      getsockname(s2, (struct sockaddr *) &myname, &myname_len);
      printf("The TCP connection is:\n");
      printf("========================\n");
      printf("My network address:\n");
      printf("  sin_addr.s_addr = %u\n", myname.sin_addr.s_addr);
      printf("  sin_port        = %u\n", myname.sin_port);

      /* -------------------------------------------
	 Print info of peer socket
	 ------------------------------------------- */
      myname_len = sizeof(myname);
      getpeername(s2, (struct sockaddr *) &myname, &myname_len);
      printf("The peer socket (client) network address:\n");
      printf("  sin_addr.s_addr = %u\n", myname.sin_addr.s_addr);
      printf("  sin_port        = %u\n\n", myname.sin_port);

      printf("\n\nNow forking a child...\n");

      /* ---------------------
	 fork()
	 --------------------- */
      if ( fork() == 0 )
      {
         /* ===============================
   	    Child process
   	    ================================ */
	 close(s1);                     // Listen socket

         /* =========================================
            Use data socket and comm. with client
            ========================================= */
         while (read(s2, &c, 1) > 0)
          { putchar(c);
	    fflush(stdout);
          }
         close(s2);
         printf("\n\n...Done...\n\n");
	 exit(0);
      }
      else
      {
	 close(s2);
      }
    }
}