/* These routines simplifies the creation of tcp streaming sockets, both 
   client and server
*/

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

/* The following function opens a client-side socket to a server.  It returns
   a file descriptor on success and -1 on failure.  The address specified can
   be either an ip address or a domain name
*/

int connectTo(char *address, unsigned short port)
{  int cfd;   // socket file descriptor
   int socklen, result;
   struct sockaddr_in saddr;  // server address structure
   struct hostent *hostinfo = NULL;

   cfd = socket(AF_INET,SOCK_STREAM,0);
   saddr.sin_family = AF_INET;
   saddr.sin_port = htons(port);
   if ((*address >= '0') && (*address <= '9'))
     saddr.sin_addr.s_addr = inet_addr(address);
   else   // dns lookup
       {   
	   hostinfo = gethostbyname(address);
	   saddr.sin_addr.s_addr = 
	       inet_addr(inet_ntoa(*(struct in_addr *)*(hostinfo->h_addr_list)));
	   //printf("addr is %s\n",inet_ntoa(saddr.sin_addr));
       }

   result = connect(cfd,(struct sockaddr*)&saddr,sizeof(saddr));
   if (result < 0) return -1; else return cfd;
}


/* a server-side socket requires two steps: */

/* 1. creatListener creates a server socket, binds it to a specified port.  
   Returns server socket if sucessful, -1 if bind failed */

int creatListener(unsigned short port)
{
  int sfd, result;
  struct sockaddr_in saddr;
  saddr.sin_family = AF_INET;
  saddr.sin_port = htons(port);
  saddr.sin_addr.s_addr = htonl(INADDR_ANY);
  sfd = socket(AF_INET,SOCK_STREAM,0);
  result = 1;
  setsockopt(sfd,SOL_SOCKET,SO_REUSEADDR,&result,sizeof(int));
  result = bind(sfd,(struct sockaddr*)&saddr,sizeof(saddr));
  if (result < 0) return -1;
  listen(sfd,32);   // sets wait queue to 32 connections
  return sfd;
}

/* 2. listen for a client connection on a server socket created with creatListener.
   returns communication socket file descriptor if success, <0 on error. */

int listenOn(int sfd)
{  int cfd;
   int slen;
   struct sockaddr_in clientinfo;  /* to be discarded here for simplicity */
   slen = sizeof(clientinfo);
   cfd = accept(sfd,(struct sockaddr*)&clientinfo,&slen);
   return cfd;
}