/*************************************************************************/
/* This program creates a well-known Internet domain socket.             */
/* Each time it accepts a connection, it forks a child to print          */
/* out a message from the client. It then goes on to accept new          */
/* connections. The child executes recho.                                */
/* To execute this program :                                             */
/*                                                                       */
/* At the local  machine:                                                */
/* 1. cc -o ex6a ex6a.c OR gcc -o ex6a ex6a.c -lsocket                   */ 
/* 2. cc -o recho ex6b.c OR gcc -o recho ex6b.c                          */
/*                                                                       */
/* At the remote machine:                                                */
/* 3. cc -o ex6c ex6c.c OR gcc -o ex6c ex6c.c -lsocket -lnsl             */ 
/* (-lsocket and -lnsl may not be required for gcc in all machines)      */
/*                                                                       */
/* local> ex6a (or ./ex6a)                                               */
/*         socket has port 1892                                          */
/*                      remote> ex6c (or ./ex6c) local.cs.pitt.edu 1892  */
/* (where local.cs.pitt.edu represents the hostname running ex6a, such   */ 
/*   as unixs4.cis.pitt.edu)                                             */
/*************************************************************************/

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

main()
{
struct sockaddr_in local;
int sk, len=sizeof(local),rsk;

/* Create an internet domain stream socket */
sk=socket(AF_INET,SOCK_STREAM,0);

/*Construct and bind the name using default values*/
local.sin_family=AF_INET;
local.sin_addr.s_addr=INADDR_ANY;
local.sin_port=0;
bind(sk,(struct sockaddr *)&local,sizeof(local));

/*Find out and publish socket name */
getsockname(sk,(struct sockaddr *)&local,&len);
printf("Socket has port %d\n",local.sin_port);

/* Start accepting connections */
/*Declare willingness to accept a connection*/
listen(sk,5); 
while(1) {
  rsk=accept(sk,0,0);/*Accept new request for a connection*/

  if(fork()==0) /*Create one child to serve each client*/
   {
    dup2(rsk,0); /*Connect the new connection to "stdin"*/
    execl("recho","recho",0);
   }
  else
    close(rsk);
  }
}