/* http://www.linuxhowtos.org/C_C++/socket.htm */

#include <stdio.h>
#include <stdlib.h>    /* atoi */  
#include <unistd.h>

#include <strings.h>   /* bzero */
#include <arpa/inet.h> /* htons */

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>

#define BUFFER_SIZE 256
#define BACKLOG 5 /* defines the maximum length to which the queue of pending connections. */

int main(int argc, char **argv){
	
	if(argc != 3){
		fprintf(stderr, "Usage: %s <PORT> <FILE_TO_SEND> \n", argv[0]);
		exit(EXIT_FAILURE);
	}

	int socketFD, newsocketFD; /* file descriptors. */
	int port = atoi(argv[1]); /* port number. */
	socklen_t clientSize /* size of the address of the client. */;
	int n; /* number of characters read or written. */
	char buffer[BUFFER_SIZE]; /* server reads from the socket into this buffer. */
	struct sockaddr_in serv_addr, cli_addr;

	socketFD = socket(AF_INET, SOCK_STREAM, 0); /* create an endpoint for communication. */
	if(socketFD < 0){
		fprintf(stderr, "Socket doesn't opening. \n");
		exit(EXIT_FAILURE);
	}

	bzero((char *) &serv_addr, sizeof(serv_addr)); /* sets all values in serv_addr to zero. */

	serv_addr.sin_family = AF_INET; /* code for the address family. */
    serv_addr.sin_port = htons(port); /* convert the port to network byte order.*/
    serv_addr.sin_addr.s_addr = INADDR_ANY; /* IP address of the host. */

    if(bind(socketFD, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0){ /* binds a socket to an address. */
		fprintf(stderr, "Socket doesn't binds to an address. \n");
		exit(EXIT_FAILURE);
	}

	listen(socketFD, BACKLOG); /* listen for connections on a socket. */


	clientSize = sizeof(cli_addr);
	newsocketFD = accept(socketFD, (struct sockaddr *) &cli_addr, &clilen); /* accept a connection on a socket. */
	if (newsocketFD < 0){
		fprintf(stderr, "Socket doesn't accept a new connection. \n");
		exit(EXIT_FAILURE);
	}

	bzero(buffer, BUFFER_SIZE); /* sets all values in buffer to zero. */

	n = read(newsocketFD, buffer, BUFFER_SIZE - 1); /* read from a file descriptor. */

	if(n < 0){
		fprintf(stderr, "Socket doesn't read to the client socket. \n");
		exit(EXIT_FAILURE);
	}

	printf("Here is the message: %s\n", buffer);

	n = write(newsocketFD, "I got your message", 18); /* write to a file descriptor. */

	if(n < 0){
		fprintf(stderr, "Socket doesn't write to the client socket. \n");
		exit(EXIT_FAILURE);
	}

	/* close a file descriptor. */
	close(newsocketFD);
    close(socketFD);

	return 0;
}