/*
NAME:       TCPServer
SYNOPSIS:    TCPServer  [Port_number]
DESCRIPTION:  The program creates a TCP socket in the inet 
              listen for connections from TCPClients, accept
              clients into private sockets. It uses select to attend
	      clients' requests as they come.

*/

#include <stdio.h>
#include <errno.h>
#include <sys/time.h>

#include <sys/param.h>
#include <sys/socket.h>
#include <sys/file.h>
#include <stdlib.h>

#include <netinet/in_systm.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/ip_icmp.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <string.h>
#include <stdlib.h>

#define MAXHOSTNAME 80
#define BUF_SIZE 500

void reusePort(int sock);  
int EchoServe(int psd);


int main(int argc,  char *argv[]) 
{
    fd_set readfds, readfdsCopy;
    int n,i;
    int sockList[64], lastSock=0;
    struct addrinfo hints, *result, *rp;
    struct addrinfo hints_local, *result_local;
    int sfd, s, ns;
    struct sockaddr_storage from_addr;
    socklen_t from_addr_len;
    ssize_t nread;
    char buffer[BUF_SIZE];
    char ThisHost[80];
  

  if (argc != 2) {
         fprintf(stderr, "Usage: %s port\n", argv[0]);
         exit(EXIT_FAILURE);
    }

    gethostname(ThisHost, MAXHOSTNAME);
    /*Obtain address(es) matching localhost/localport*/
    memset(&hints_local, 0, sizeof(hints_local));
    hints_local.ai_family = AF_INET; //IPv4
    hints_local.ai_socktype = SOCK_STREAM; //TCP
    hints_local.ai_flags = AI_PASSIVE;

    if (getaddrinfo(ThisHost, argv[1], &hints_local, &result_local) != 0)
    {
        fprintf(stderr, "getaddrinfo error\n");
        exit(EXIT_FAILURE);
    }

    printf("----EchoServer/TCP running at host NAME: %s\n", ThisHost);
    printf("(EchoServer/TCP INET ADDRESS is: %s )\n", inet_ntoa(((struct sockaddr_in*)result_local->ai_addr)->sin_addr));
    printf("Server Port is: %s \n", argv[1]);

    memset(&hints, 0, sizeof(hints));

   hints.ai_family = AF_INET; //IPv4
   hints.ai_socktype = SOCK_STREAM; //TCP
   hints.ai_flags = AI_PASSIVE; //For wildcard IP address

   if ((getaddrinfo(NULL, argv[1], &hints, &result)) != 0)
   {
      fprintf(stderr, "getaddrinfo error\n");
      exit(EXIT_FAILURE);
   }

   /* getaddrinfo() returns a list of address structures.
    Try each address until we successfully bind.
    If socket (or bind) fails, we (close the socket
    and) try the next address. */ 

   for (rp = result; rp != NULL; rp = rp -> ai_next)
    {
        s = socket(rp->ai_family, rp->ai_socktype, rp->ai_protocol);
        
        reusePort(s);
        
        if (s == -1)
        {
            continue;
        }
        if (bind(s, rp -> ai_addr, rp -> ai_addrlen) == 0)
        {
            break; //Success
        }
        close(s);        
    }
    
    freeaddrinfo(result); //No longer needed

    if (rp == NULL)
    {
        fprintf(stderr, "Could not bind\n");
        exit(EXIT_FAILURE);
    }

  listen(s,4);
  from_addr_len = sizeof(from_addr);
  FD_ZERO(&readfdsCopy);
  FD_SET(s,&readfdsCopy);
  
  for(;;){
    memcpy(&readfds, &readfdsCopy, sizeof(fd_set));
    n = select(FD_SETSIZE, &readfds, (fd_set *) 0, (fd_set *) 0, NULL);
    if (n > 0) {
      if (FD_ISSET(s, &readfds)) {
        printf("Accepting a new connection...\n");
        sockList[lastSock++] = accept(s, (struct sockaddr *) &from_addr, &from_addr_len);
        FD_SET(sockList[lastSock-1], &readfdsCopy);
      }
      for (i=0; i < lastSock; i++) {
        if (FD_ISSET(sockList[i], &readfds))
          if (EchoServe(sockList[i]) < 0) {
            FD_CLR(sockList[i], &readfdsCopy);
            close (sockList[i]);
            sockList[i] = sockList[--lastSock];
            i--;
            printf("Number of current clients: %d\n", lastSock);
          }
      }
    }
  }
}
int EchoServe(int psd)
{
  char buf[512];
  int rc;

  /*      get data from  clients and send it back */
  for(;;){
    printf("\n...server is waiting...\n");
    if( (rc=read(psd, buf, sizeof(buf))) < 0)
      perror("receiving stream  message");
    if (rc > 0){
      buf[rc]='\0';
      printf("Received: %s\n", buf);
      if (send(psd, buf, rc, 0) <0 )
        perror("sending stream message");
      return(1);
    }
    else {
      printf("Disconnected..\n");
      return(-1);
    }
  }
}
void reusePort(int s)
{
  int one=1;

  if ( setsockopt(s,SOL_SOCKET,SO_REUSEADDR,(char *) &one,sizeof(one)) == -1 )
  {
    printf("error in setsockopt,SO_REUSEPORT \n");
    exit(-1);
  }
}