/* Server program for Internet TCP sockets */

/* Server starts, creates and binds a socket */
/* and waits for a request for a connection */

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

#define PORT  7000 /* Port of this server */
#define SIZE sizeof(struct sockaddr_in)

int
main(void)
{
    char buf[1024];
    int n, s, ns, len;
    struct sockaddr_in srv = {AF_INET, PORT, INADDR_ANY};
    struct sockaddr_in cli; /* For client's address */
    int cli_len = SIZE;
     
    printf("TCP SERVER: starting ...\n");
    
    /*
     * Create the Internet socket, of SOCK_STREAM type.
     */
    if ((s = socket(AF_INET, SOCK_STREAM, 0)) < 0) 
        {
        perror("socket problem");
        exit(1);
        }


    /*
     * For simplicity, use the IP address as the OS selects.
     * It is more preferable to set a specific IP address
     * which must be known to all clients...
     */


    /*
     * Bind the socket to the the IP address of this host.
     */
    if (bind(s, (struct sockaddr *) &srv, SIZE) < 0) 
        {
        perror("bind problem");
        exit(1);
        }
       
     /* Set the size of requests queue */
     if (listen(s, 5) < 0)
     {perror("listen problem"); exit(1);}

     /* Now establish a connection if there is a request */
     /* for a connection from a client */
     /* A new socket descriptor will be created for this connection */
     /* The server may continue listening on the old socket descriptor */
     /* for new request for a connection */
     
 while(1)
 {
     ns = accept(s, (struct sockaddr *) &cli, &len);
     if (ns < 0) {perror ("accept problem"); exit(1);}

    /*
     * Now read from the new socket ns
     */
    n = recv(ns, buf, sizeof(buf), 0);
    if (n < 0) {perror("recv problem"); exit(1);}

    write(1, buf, n);
    
    /* Sending a reply to client */
    send (ns, "This is a reply from server\n",28,0);
    printf ("TCP SERVER: a reply is sent...\n");


    close (ns);
 }  
  
}