/*
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 <netinet/in_systm.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/ip_icmp.h>
#include <netdb.h>


#define MAXHOSTNAME 80
void reusePort(int sock);   

main( argc, argv )
int argc;
char *argv[];
{
  int   s, ss;
  struct   sockaddr_in server;
  struct sockaddr_in from;
  int fromlen;
  int length;

  fd_set readfds, readfdsCopy;
  int n,i;
  int sockList[64], lastSock=0;
  

  /* Construct name of socket to send to. */
  server.sin_family = AF_INET;
  server.sin_addr.s_addr = htonl(INADDR_ANY);
  if (argc == 2)
      server.sin_port = htons(atoi(argv[1])); 
  else
      server.sin_port = htons(0);  

  s = socket (AF_INET,SOCK_STREAM,0); 
  reusePort(s);

  if ( bind( s, (struct sockaddr *)&server, sizeof(server) ) ) {
    close(s);
    perror("binding name to stream socket");
    exit(-1);
  }

  length = sizeof(server);
  if ( getsockname (s, (struct sockaddr *)&server,&length) ) {
    perror("getting socket name");
    exit(0);
  }

  printf("Server Port is: %d\n", ntohs(server.sin_port));

  listen(s,4);
  fromlen = sizeof(from);
  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, &fromlen);
        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);
  }
}