/**********************************************************************
 * server.c
 *
 *  SERVER CODE 
 *
 * from https://www.programminglogic.com/
 *      example-of-client-server-program-in-c-using-sockets-and-tcp/
 * 
 * ... with various minor modifications by Jim Mahoney on Nov 2018.
 *********************************************************************/

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

/* Pick a port to use for this client/server connection.
   The client will need to use this same port.
   It's an arbitrary number between 1024 and 65535 (16 bit unsigned). */
/* The low ports are reserved for system use; google "port numbers". */
#define PORT 7891

/* And pick an arbitrary number of connections which can be waiting. */
#define MAX_CONNECTIONS 5

#define BUFFER_SIZE 1024

/* localhost */
#define LOCALHOST "127.0.0.1"

/* shannon.marlboro.college */
#define SHANNON "96.126.107.158"

int main(){
  char buffer[BUFFER_SIZE];
  int listen_socket;
  int connect_socket;
  struct sockaddr_in address;
  struct sockaddr_storage storage;
  socklen_t address_size = sizeof(struct sockaddr_in);

  char* message = "The server says 'Hi there!'";
  
  /*---- Create the socket. The three arguments are: ----
      1) Internet domain 
      2) Stream socket 
      3) Default protocol (TCP in this case)   */
  listen_socket = socket(PF_INET, SOCK_STREAM, 0);

  /*---- Configure settings of the server address struct ----*/
  
  /* Address family = Internet */
  address.sin_family = AF_INET;
  
  /* Set port number, using htons function to use proper byte order */
  address.sin_port = htons(PORT);
  
  /* Set IP address to localhost */
  /* address.sin_addr.s_addr = inet_addr(HOST); */
  /* ... or shannon.marlboro.college */
  address.sin_addr.s_addr = inet_addr(SHANNON);
  
  /* Set all bits of the padding field to 0 */
  memset(address.sin_zero, '\0', sizeof(address.sin_zero));

  /*---- Bind the address struct to the socket ----*/
  bind(listen_socket, (struct sockaddr *) &address, sizeof(address));

  /*-- Listen on the socket, with 5 max connection requests queued --*/
  if(listen(listen_socket, MAX_CONNECTIONS)==0) {
    printf("Server: listening on port %d ...\n", PORT);
  }else {
    printf("Error!\n");
    return 0;  /* Something went wrong - bail out. */
  }

  /*-- Accept call creates a new socket for the first queued connection. --*/
  /* This is a "blocking call" - execution stops here and waits. */
  /* See e.g. http://manpages.ubuntu.com/manpages/bionic/man2/accept.2.html */
  connect_socket = accept(listen_socket,
			  (struct sockaddr *) &storage,
			  &address_size);
  printf("Server: connection established.\n");

  /*---- Send message to the socket of the incoming connection ----*/
  strcpy(buffer, message);
  send(connect_socket, buffer, strlen(message) + 1, 0);
  printf("Server: message sent.\n");

  printf("Server exiting.\n");
  close(connect_socket);
  close(listen_socket);
  return 0;
}