server.c

/*
** server.c -- a stream socket server demo
*/

#include <stdio.h>
#include <unistd.h>
#include <stdbool.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <sys/wait.h>
#include <signal.h>
#define MAXDATASIZE 100 // max number of bytes we can get at once 

#define PORT "3490"  // the port users will be connecting to

#define BACKLOG 10	 // how many pending connections queue will hold
#define NO_OF_USER 21 // 20 student + 1 instructor
void sigchld_handler(int s)
{
	(void)s; // quiet unused variable warning

	// waitpid() might overwrite errno, so we save and restore it:
	int saved_errno = errno;

	while(waitpid(-1, NULL, WNOHANG) > 0);

	errno = saved_errno;
}


// get sockaddr, IPv4 or IPv6:
void *get_in_addr(struct sockaddr *sa)
{
	if (sa->sa_family == AF_INET) {
		return &(((struct sockaddr_in*)sa)->sin_addr);
	}

	return &(((struct sockaddr_in6*)sa)->sin6_addr);
}

const char* getfield(char* line, int num)
{
    const char* tok;
    for (tok = strtok(line, ",");
    		tok && *tok;
            tok = strtok(NULL, ","))
    {
        if (!--num)
            return tok;
    }
    return NULL;
}

bool verify_credentials(char *const username, char *const password){
	FILE* cred_data = fopen("user_pass.csv", "r");
	char line[NO_OF_USER];
	while (fgets(line, NO_OF_USER, cred_data))
    {
        char* tmp = strdup(line);
        if(username == getfield(tmp, 1) && password == getfield(tmp, 2)){
			return true;
		}
        free(tmp);
    }
	return false;
}

void display_marks(int client_fd, char* username){
	FILE* marks = fopen("student_marks.csv", "r");
	char line[NO_OF_USER];
	char sub_number[5];
	int sub_number_int;
	send(client_fd, "Name", 4, 0);
	send(client_fd, "        ", 8, 0);
	//send(client_fd, "\t", 1, 0);
	//send(client_fd,username,5,0);
	for(int i=0;i<5;i++){
		send(client_fd, "SUB", 3, 0);
		sub_number_int = i+1;
		char sub_no[5];
		//itoa(sub_number_int,sub_no,10);
		snprintf (sub_no, sizeof(sub_no), "%d",sub_number_int);
		send(client_fd, sub_no, 1, 0);
		send(client_fd, "\t", 1, 0);
	}
	send(client_fd, "AggrPer", 7, 0);
	//send(client_fd, "\n", 1, 0);
	int total_class_marks = 0;
	while (fgets(line, NO_OF_USER, marks))
    {
		//send(client_fd,username,5,0);
        //printf("asdfsad%s",username);
        //exit(1);
        char* tmp = strdup(line);
        printf("%s", tmp);
        printf("%lu", sizeof(tmp));
        
		if(strcmp(username, "instructor")==0 || strcmp(username, getfield(tmp, 1))==0){
			
			send(client_fd,"adfsdf",6,0);
			send(client_fd, getfield(tmp, 1), 12, 0);
			send(client_fd, "\t", 1, 0);
			send(client_fd,"asdfsdfe",6,0);
			int total_sub = 0;
			for(int i=0;i<5;i++){
				total_sub = total_sub + atoi(getfield(tmp,i+2));
				send(client_fd, getfield(tmp, i+2), 3, 0);
				send(client_fd, "  ", 2, 0);
				send(client_fd, "\t", 1, 0);
			}
			char aggrPerBuf[10];
			total_class_marks = total_class_marks + total_sub;
			gcvt((float)total_sub/5.0, 4, aggrPerBuf);
			send(client_fd, &aggrPerBuf[0], 5, 0);
			send(client_fd, " ", 1, 0);
			send(client_fd, "\n", 1, 0);
		}
		if(strcmp(username, "instructor")==0){
			char aggrPerBuf[10];
			gcvt((float)total_class_marks/20, 5, aggrPerBuf);
			send(client_fd, "Class Average : ", 16, 0);
			send(client_fd, &aggrPerBuf[0], 6, 0);
			send(client_fd, "\n", 1, 0);
		}
        free(tmp);
    }
}


int main(void)
{
	int sockfd, new_fd;  // listen on sock_fd, new connection on new_fd
	struct addrinfo hints, *servinfo, *p;
	struct sockaddr_storage their_addr; // connector's address information
	socklen_t sin_size;
	struct sigaction sa;
	int yes=1;
	char s[INET6_ADDRSTRLEN];
	int rv;
	char buf[100];
	int numbytes = 0;
	memset(&hints, 0, sizeof hints);
	hints.ai_family = AF_UNSPEC;
	hints.ai_socktype = SOCK_STREAM;
	hints.ai_flags = AI_PASSIVE; // use my IP

	if ((rv = getaddrinfo(NULL, PORT, &hints, &servinfo)) != 0) {
		fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
		return 1;
	}

	// loop through all the results and bind to the first we can
	for(p = servinfo; p != NULL; p = p->ai_next) {
		if ((sockfd = socket(p->ai_family, p->ai_socktype,
				p->ai_protocol)) == -1) {
			perror("server: socket");
			continue;
		}

		if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &yes,
				sizeof(int)) == -1) {
			perror("setsockopt");
			exit(1);
		}

		if (bind(sockfd, p->ai_addr, p->ai_addrlen) == -1) {
			close(sockfd);
			perror("server: bind");
			continue;
		}

		break;
	}

	freeaddrinfo(servinfo); // all done with this structure

	if (p == NULL)  {
		fprintf(stderr, "server: failed to bind\n");
		exit(1);
	}

	if (listen(sockfd, BACKLOG) == -1) {
		perror("listen");
		exit(1);
	}

	sa.sa_handler = sigchld_handler; // reap all dead processes
	sigemptyset(&sa.sa_mask);
	sa.sa_flags = SA_RESTART;
	if (sigaction(SIGCHLD, &sa, NULL) == -1) {
		perror("sigaction");
		exit(1);
	}

	printf("server: waiting for connections...\n");

	while(1) {  // main accept() loop
		sin_size = sizeof their_addr;
		new_fd = accept(sockfd, (struct sockaddr *)&their_addr, &sin_size);
		if (new_fd == -1) {
			perror("accept");
			continue;
		}

		inet_ntop(their_addr.ss_family,
			get_in_addr((struct sockaddr *)&their_addr),
			s, sizeof s);
		printf("server: got connection from %s\n", s);

		if (!fork()) { // this is the child process
			close(sockfd); // child doesn't need the listener
			//if (send(new_fd, "Hello Mr.", 9, 0) == -1)
			//	perror("send");
			bool login = false;
			char username[20];
			char password[20];
			char buffer_Recv[MAXDATASIZE];
			//int buf_len=0;
			bool recv_open = true;
			bool send_open = false;
			bool process_open=false;
			bool wait_user=false;
			bool wait_pass=false;

			send(new_fd, "Menu\n login\n show_marks\n logout ", 50, 0);
			send(new_fd, "\n\r", 2, 0);
			//Display_Menu(new_fd, login, username);
			

			while(1){
				if(!process_open){
					if ((numbytes = recv(new_fd, buffer_Recv, MAXDATASIZE-1, 0)) == -1) {
						perror("recv");
						printf("error");
						exit(1);
					}
					//send(new_fd,"hihi",4,0);
					//send(new_fd,buffer_Recv,numbytes,0);
					//send(new_fd,&numbytes,4,0);
					//printf( "ddd %s as %d  sss",buffer_Recv,numbytes);
					//if(wait_pass){
					//	exit(0);
					//}
					if(numbytes>1)
					{
						//send(new_fd,"bobo",4,0);
						process_open=true;
						recv_open=false;
					}
				}
				else if(process_open)
				{
					if(strcmp(buffer_Recv, "login")==0 && !login){
						send(new_fd, "Enter Username: ", 16, 0);
						send(new_fd, "\n\r", 2, 0);
						wait_user=true;

					}
					else if(wait_user)
					{

						memcpy(&username[0], &buffer_Recv[0], numbytes);
						username[numbytes] = '\0';
						send(new_fd, "Enter password: ", 16, 0);
						send(new_fd, "\n\r", 2, 0);
						wait_user=false;
						wait_pass=true;
					}
					else if(wait_pass)
					{
						memcpy(&password[0], &buffer_Recv[0], numbytes);
						password[numbytes] = '\0';
						
						if(verify_credentials(username,password)){
							login = true;
							send(new_fd, "Logged In Successfully", 22, 0);
							send(new_fd, "\n\r", 2, 0);
						}
						else{
							login = true;//change this 
							memset(&buf[0], 0, MAXDATASIZE);
							//memset(&username[0], 0, sizeof(username));
							send(new_fd, "Invalid Entry", 13, 0);
							send(new_fd, "\n\r", 2, 0);
						}
						wait_pass=false;

					}

					else if(strcmp(buffer_Recv, "logout")==0 && login){
						login = false;
						memset(&buffer_Recv[0], '\0', MAXDATASIZE);
						memset(&username[0], '\0', sizeof(username));
						memset(&password[0], '\0', sizeof(password));
						send(new_fd, "logged out!!", 15, 0);
						send(new_fd, "\n\r", 2, 0);
					}

					else if(strcmp(buffer_Recv, "show_marks")==0 && login){

						display_marks(new_fd, username);
						send(new_fd, "\n\r", 2, 0);
					}

					else{
						send(new_fd, "Invalid Request", 15, 0);
						send(new_fd, "\n\r", 2, 0);
					}
					process_open=false;
					numbytes=0;

				}

				
								
			}
			close(new_fd);
			exit(0);
		}
		close(new_fd);  // parent doesn't need this
	}

	return 0;
}