newClient.c

#include <stdio.h>      /* for printf() and fprintf() */
#include <sys/socket.h> /* for socket(), connect(), sendto(), and recvfrom() */
#include <arpa/inet.h>  /* for sockaddr_in and inet_addr() */
#include <stdlib.h>     /* for atoi() and exit() */
#include <string.h>     /* for memset() */
#include <unistd.h>     /* for close() */
#include <sys/mman.h>   /* for mmap() */
#include <string.h>     /* for string strcpy() and strlen() */ 

/*Global Variables*/
int userID;         /* The user's ID */
int sock;           /* Socket descriptor */ 
struct sockaddr_in echoServAddr; /* Echo server address */
unsigned short echoServPort;     /* Echo server port */

/* Client Message Struct */
struct ClientMessage{
	enum {Login, Post, Activate, Subscribe, Unsusbscribe, Logout }
	request_Type;                                    /* same size as an unsigned int */
	unsigned int UserID;                             /* unique client identifier */
	unsigned int LeaderID;                           /* unique client identifier */
	char message[100];                               /* text message */
};                                      /* an unsigned int is 32 bits = 4 bytes */

/* Server Message Struct */
struct ServerMessage{
	unsigned int LeaderID;                           /* unique client identifier */
	char message[100];                               /* text message */
};                                      /* an unsigned int is 32 bits = 4 bytes */

void DieWithError(char *errorMessage);  /* External error handling function */
void signIn();						    /* Client Signs in */
void signOut();						    /* Client Signs Out */
void follow(); 						    /* Client follows a Leader */
void unfollow(); 					    /* Client follows a Leader */
void get_msg(); 						/* Gets saved messages from server */
void send_msg(); 						/* Send a message to followers */
void send_to_server(struct ClientMessage *msg); /*Sends the ClientMessage to the server */
void run_client(); 						/* User Driven Menu To Run Program */


int main(int argc, char *argv[])
{
    struct sockaddr_in fromAddr;     	/* Source address of client */
    unsigned int fromSize;          	/* In-out of address size for recvfrom() */
    char servIP[16];                    /* IP address of server */
    struct ServerMessage server_MSG;    /* Buffer for receiving messages from server */
    char serverport[10]; 				/* Port of the server */
    
    /*Prompt user for an ID, Server IP, Port */
    printf("Please Enter Your User ID: ");
	scanf("%d",&userID);
	printf("Your ID is: %d\n",userID);  
    printf("Please enter the server IP Address: ");
    scanf("%s",servIP);
    printf("Please enter the server's port number: ");
    scanf("%s",serverport);
    echoServPort = atoi(serverport); 	/* Convert user response to int */
    
    
    /* Create a datagram/UDP socket */
    if ((sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0)
        DieWithError("socket() failed");
    
    /* Construct the server address structure */
    memset(&echoServAddr, 0, sizeof(echoServAddr));    /* Zero out structure */
    echoServAddr.sin_family = AF_INET;                 /* Internet addr family */
    echoServAddr.sin_addr.s_addr = inet_addr(servIP);  /* Server IP address */
    echoServAddr.sin_port   = htons(echoServPort);     /* Server port */
    
    /* Recv a response handled by child node */
	fromSize = sizeof(fromAddr);
	if (fork() == 0){
    	int x;
  	 	for (;;){
			recvfrom(sock, &server_MSG, sizeof(struct ServerMessage), 0,(struct sockaddr *) &fromAddr, &fromSize);
			if (echoServAddr.sin_addr.s_addr != fromAddr.sin_addr.s_addr)
			{
				fprintf(stderr,"Error: received a packet from unknown source.\n");
				exit(1);
			}
			printf("%d said: %s",server_MSG.LeaderID,server_MSG.message);


    	}
	   exit(0);
	}    
    /* Signs in user, retrieves stored messages, launches user menu */
    signIn();
    get_msg();
    run_client();
    /* closes socket and exits when user quits */
    close(sock);
    exit(0);
}
/* Signs in client */
void signIn()
{
	struct ClientMessage c;
	c.request_Type = 0;
	c.UserID = userID;
	printf("Signing in\n");
	send_to_server(&c);
}
/* Client signs Out. */
void signOut()
{
	struct ClientMessage c;
	c.request_Type = 5;
	c.UserID = userID;
	printf("Signing out\n");
	send_to_server(&c);
} 
/* Client follows a Leader. */
void follow()  
{
	printf("Who would you like to follow:\n");
	struct ClientMessage c;
	c.request_Type = 3;
	c.UserID = userID;
	scanf("%d", &c.LeaderID);
	printf("You have followed %d\n", c.LeaderID);
	send_to_server(&c);
}
/* Client unfollows a Leader */
void unfollow()
{
	printf("Who would you like to unfollow:\n");
	struct ClientMessage c;
	c.request_Type = 4;
	c.UserID = userID;
	scanf("%d", &c.LeaderID);
	printf("You have unfollowed %d\n", c.LeaderID);
	send_to_server(&c);
} 
/* Request any stored messages from the server */
void get_msg()
{
	struct ClientMessage c;
	c.request_Type = 2;
	c.UserID = userID;
	send_to_server(&c);
	return;
}
/* Send a message to followers */
void send_msg()
{
	struct ClientMessage c;
	fseek(stdin,0,SEEK_END);	/* Clear stdin */
	printf("Enter the message you want to send:\n");
	fgets(c.message, 100, stdin);
	fseek(stdin,0,SEEK_END);	/* Clear stdin */
	if(strlen(c.message) >= 100)
	{
		printf("Your message must be under 100 characters\n");
		return;
	}
	 c.UserID = userID;
	 c.request_Type = 1;
	 send_to_server(&c);
	 return;
} 
/* This function receives a completed ClientMessage and sends it out to the server */
void send_to_server(struct ClientMessage *msg)
{
	    /* Send the message to the server */
		sendto(sock, msg, sizeof(*msg), 0, (struct sockaddr *) &echoServAddr, 
			sizeof(echoServAddr));
	
}
/* runs the user driven menu until the user quits with Sign Out */
void run_client()
{
	int selection;
	/* Loop with switch statement drives the user interface User keeps entering
	   options until they quit by signing out */
	do
	{
		printf("Please Select an Option\n");
		printf("1-Follow a User\n");
		printf("2-Unfollow a User\n");
		printf("3-Send Message\n");
		printf("4-Sign Out & Quit\n");
		scanf("%d",&selection);
	
		switch(selection)
		{
			case 1: //follow a user
			{
				follow();
				break;
			}
			case 2: //unfollow a user
			{
				unfollow();
				break;
			}
			case 3: //Send message
			{
				send_msg();
				break;
			}
			case 4: //log out
			{
				signOut();
				break;
			}		
			default: //Error for incorrect entries
				printf("Your entry is invalid. Please try again\n");
		}
	}while(selection != 4);  /* do until user signs out */
}