/*
	File		: tcp_uppercase_echo_client.c
	Programmer	: Nasif Ekiz
	Date		: 
	Description	: This is the client side of a TCP client/server application
	where the client sends a message to the server and server responds with an 
	modified echo message where the incomming message is converted to all uppercase
	message. The client prints the modified incomming message on the screen and
	closes the socket.
*/

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

#define STRING_SIZE 1024

int main(void) {
	
	int sock_client;			// client socket
	
	struct sockaddr_in server_addr; 	// structure that stores server address

	struct hostent * server_hp; 		// structure to store server's IP address
	
	char server_hostname[STRING_SIZE]; 	// server's hostname 
	unsigned short server_port;		// server's port
	
	char sentence[STRING_SIZE]; 		// send message
	char modifiedSentence[STRING_SIZE];	// receive message
	unsigned int msg_len;			// length of message
	int bytes_sent, bytes_recd;		// number of bytes sent and received		

	/* 
		open a socket
		AF_INET		: IPv4 protocol
		SOCK_STREAM	: stream socket
		IPPROTO_TCP	: TCP transport protocol
	*/
	if ((sock_client = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0) {
		perror("Client : can't open stream socket");
		exit(1);
	} 

	// initialize server address information
	printf("Enter hostname of server : ");
	scanf("%s", server_hostname);					// get host name
	if ((server_hp = gethostbyname(server_hostname)) == NULL ) {	// make a DNS look up query 
		perror("Client : invalid server hostname");
		close(sock_client);
		exit(1);
	}

	printf("Enter port number of server: ");
	scanf("%hu", &server_port);					// get server's port number 

	// clear server address structure and initialize with server address
	memset(&server_addr, 0, sizeof(server_addr));
	server_addr.sin_family = AF_INET;
	
	// copy the server's IP address obtained by DNS look up into the server address structure
	memcpy((char *)&server_addr.sin_addr, server_hp->h_addr, server_hp->h_length);
	server_addr.sin_port = htons(server_port);	// convert port number from host byte order 
							// to network byte order and assign it to 
							// server's port number

	// connect to server
	if (connect(sock_client, (struct sockaddr *) &server_addr, sizeof(server_addr)) < 0) {
		perror("Client : can't connect to server");
		close(sock_client);
		exit(1);
	}

	// user interface
	printf("Please input a sentence :\n");
	scanf("%s", sentence);
	msg_len = strlen(sentence) + 1;		// send message length

	// send message
	bytes_sent = send(sock_client, sentence, msg_len, 0);
	
	// get response from server
	bytes_recd = recv(sock_client, modifiedSentence, STRING_SIZE, 0);
	
	// print incomming echo message from server
	printf("\nThe response from server is : \n");
	printf("%s\n\n", modifiedSentence);

	// close the socket
	close(sock_client);
}