tftp_c.c

/**
 * tftp_c.c - tftp client
 */
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include "utility.h"

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);
}

//CHECKS FOR TIMEOUT
int check_timeout(int sockfd, char *buf, struct sockaddr_storage their_addr, socklen_t addr_len){
	fd_set fds;
	int n;
	struct timeval tv;

	// set up the file descriptor set
	FD_ZERO(&fds);
	FD_SET(sockfd, &fds);

	// set up the struct timeval for the timeout
	tv.tv_sec = TIME_OUT;
	tv.tv_usec = 0;

	// wait until timeout or data received
	n = select(sockfd+1, &fds, NULL, NULL, &tv);
	if (n == 0){
		printf("timeout\n");
		return -2; // timeout!
	} else if (n == -1){
		printf("error\n");
		return -1; // error	
	}

	return recvfrom(sockfd, buf, MAXBUFLEN-1 , 0, (struct sockaddr *)&their_addr, &addr_len);
}

int main(int argc, char* argv[]){
	int sockfd;
	struct addrinfo hints, *servinfo, *p;
	int rv;
	int numbytes;
	char buf[MAXBUFLEN];
	char s[INET6_ADDRSTRLEN];
	struct sockaddr_storage their_addr;
	socklen_t addr_len;
		
	if(argc != 4){// CHECKS IF args ARE VALID
		fprintf(stderr,"USAGE: tftp_c GET/PUT server filename\n");
		exit(1);
	}

	char *server = argv[2];// server address
	char *file = argv[3]; // file name on which operation has to be done
	
	//===========CONFIGURATION OF CLIENT - STARTS===========
	memset(&hints, 0, sizeof hints);
	hints.ai_family = AF_UNSPEC;
	hints.ai_socktype = SOCK_DGRAM;
	if((rv = getaddrinfo(server, SERVERPORT, &hints, &servinfo)) != 0){
		fprintf(stderr, "CLIENT: getaddrinfo: %s\n", gai_strerror(rv));
		return 1;
	}
	
	// loop through all the results and make a socket
	for(p = servinfo; p != NULL; p = p->ai_next) {
		if ((sockfd = socket(p->ai_family, p->ai_socktype, p->ai_protocol)) == -1){
			perror("CLIENT: socket");
			continue;
		}
		break;
	}
	if(p == NULL){
		fprintf(stderr, "CLIENT: failed to bind socket\n");
		return 2;
	}
	//===========CONFIGURATION OF CLIENT - ENDS===========


	//===========MAIN IMPLEMENTATION - STARTS===========
	if(strcmp(argv[1], "GET") == 0 || strcmp(argv[1], "get") == 0){ //GET DATA FROM SERVER
		//SENDING RRQ
		char *message = make_rrq(file);
		char last_recv_message[MAXBUFLEN];strcpy(last_recv_message, "");
		char last_sent_ack[10];strcpy(last_sent_ack, message);
		if((numbytes = sendto(sockfd, message, strlen(message), 0, p->ai_addr, p->ai_addrlen)) == -1){
			perror("CLIENT: sendto");
			exit(1);
		}
		printf("CLIENT: sent %d bytes to %s\n", numbytes, server);

		char filename[MAX_FILENAME_LEN];
		strcpy(filename, file);
		strcat(filename, "_client");

		FILE *fp = fopen(filename, "wb");
		if(fp == NULL){ //ERROR CHECKING
			fprintf(stderr,"CLIENT: error opening file: %s\n", filename);
			exit(1);
		}
		
		//RECEIVING ACTUAL FILE
		int c_written;
		do{
			//RECEIVING FILE - PACKET DATA
			addr_len = sizeof their_addr;
			if ((numbytes = recvfrom(sockfd, buf, MAXBUFLEN-1 , 0, (struct sockaddr *)&their_addr, &addr_len)) == -1) {
				perror("CLIENT: recvfrom");
				exit(1);
			}
			printf("CLIENT: got packet from %s\n", inet_ntop(their_addr.ss_family, get_in_addr((struct sockaddr *)&their_addr), s, sizeof s));
			printf("CLIENT: packet is %d bytes long\n", numbytes);
			buf[numbytes] = '\0';
			printf("CLIENT: packet contains \"%s\"\n", buf);

			//CHECKING IF ERROR PACKET
			if(buf[0]=='0' && buf[1]=='5'){
				fprintf(stderr, "CLIENT: got error packet: %s\n", buf);
				exit(1);
			}

			//SENDING LAST ACK AGAIN - AS IT WAS NOT REACHED
			if(strcmp(buf, last_recv_message) == 0){
				sendto(sockfd, last_sent_ack, strlen(last_sent_ack), 0, (struct sockaddr *)&their_addr, addr_len);
				continue;
			}

			//WRITING FILE - PACKET DATA
			c_written = strlen(buf+4);
			fwrite(buf+4, sizeof(char), c_written, fp);
			strcpy(last_recv_message, buf);

			//SENDING ACKNOWLEDGEMENT - PACKET DATA
			char block[3];
			strncpy(block, buf+2, 2);
			block[2] = '\0';
			char *t_msg = make_ack(block);
			if((numbytes = sendto(sockfd, t_msg, strlen(t_msg), 0, p->ai_addr, p->ai_addrlen)) == -1){
				perror("CLIENT ACK: sendto");
				exit(1);
			}
			printf("CLIENT: sent %d bytes\n", numbytes);
			strcpy(last_sent_ack, t_msg);
		} while(c_written == MAX_READ_LEN);
		printf("NEW FILE: %s SUCCESSFULLY MADE\n", filename);
		fclose(fp);
	} else if(strcmp(argv[1], "PUT") == 0 || strcmp(argv[1], "put") == 0){	//WRITE DATA TO SERVER	
		//SENDING WRQ
		char *message = make_wrq(file);
		char *last_message;
		if((numbytes = sendto(sockfd, message, strlen(message), 0, p->ai_addr, p->ai_addrlen)) == -1){
			perror("CLIENT: sendto");
			exit(1);
		}
		printf("CLIENT: sent %d bytes to %s\n", numbytes, server);
		last_message = message;

		//WAITING FOR ACKNOWLEDGEMENT - WRQ
		int times;
		addr_len = sizeof their_addr;
		for(times=0;times<=MAX_TRIES;++times){
			if(times == MAX_TRIES){// reached max no. of tries
				printf("CLIENT: MAX NUMBER OF TRIES REACHED\n");
				exit(1);
			}

			// checking if timeout has occurred or not
			numbytes = check_timeout(sockfd, buf, their_addr, addr_len);
			if(numbytes == -1){//error
				perror("CLIENT: recvfrom");
				exit(1);
			} else if(numbytes == -2){//timeout
				printf("CLIENT: try no. %d\n", times+1);
				int temp_bytes;
				if((temp_bytes = sendto(sockfd, last_message, strlen(last_message), 0, p->ai_addr, p->ai_addrlen)) == -1){
					perror("CLIENT ACK: sendto");
					exit(1);
				}
				printf("CLIENT: sent %d bytes AGAIN\n", temp_bytes);
				continue;
			} else { //valid
				break;
			}
		}
		printf("CLIENT: got packet from %s\n", inet_ntop(their_addr.ss_family, get_in_addr((struct sockaddr *)&their_addr), s, sizeof s));
		printf("CLIENT: packet is %d bytes long\n", numbytes);
		buf[numbytes] = '\0';
		printf("CLIENT: packet contains \"%s\"\n", buf);

		if(buf[0]=='0' && buf[1]=='4'){
			FILE *fp = fopen(file, "rb");
			if(fp == NULL || access(file, F_OK) == -1){
				fprintf(stderr,"CLIENT: file %s does not exist\n", file);
				exit(1);
			}

			//calculating of size of file
			int block = 1;
			fseek(fp, 0, SEEK_END);
			int total = ftell(fp);
			fseek(fp, 0, SEEK_SET);
			int remaining = total;
			if(remaining == 0)
				++remaining;
			else if(remaining%MAX_READ_LEN == 0)
				--remaining;

			while(remaining>0){
				//READING FILE - DATA PACKET
				char temp[MAX_READ_LEN+5];
				if(remaining>MAX_READ_LEN){
					fread(temp, MAX_READ_LEN, sizeof(char), fp);
					temp[MAX_READ_LEN] = '\0';
					remaining -= (MAX_READ_LEN);
				} else {
					fread(temp, remaining, sizeof(char), fp);
					temp[remaining] = '\0';
					remaining = 0;
				}

				//SENDING FILE - DATA PACKET
				char *t_msg = make_data_pack(block, temp);
				if((numbytes = sendto(sockfd, t_msg, strlen(t_msg), 0, p->ai_addr, p->ai_addrlen)) == -1){
					perror("CLIENT: sendto");
					exit(1);
				}
				printf("CLIENT: sent %d bytes to %s\n", numbytes, server);
				last_message = t_msg;

				//WAITING FOR ACKNOWLEDGEMENT - DATA PACKET
				int times;
				for(times=0;times<=MAX_TRIES;++times){
					if(times == MAX_TRIES){
						printf("CLIENT: MAX NUMBER OF TRIES REACHED\n");
						exit(1);
					}

					numbytes = check_timeout(sockfd, buf, their_addr, addr_len);
					if(numbytes == -1){//error
						perror("CLIENT: recvfrom");
						exit(1);
					} else if(numbytes == -2){//timeout
						printf("CLIENT: try no. %d\n", times+1);
						int temp_bytes;
						if((temp_bytes = sendto(sockfd, last_message, strlen(last_message), 0, p->ai_addr, p->ai_addrlen)) == -1){
							perror("CLIENT ACK: sendto");
							exit(1);
						}
						printf("CLIENT: sent %d bytes AGAIN\n", temp_bytes);
						continue;
					} else { //valid
						break;
					}
				}
				printf("CLIENT: got packet from %s\n", inet_ntop(their_addr.ss_family, get_in_addr((struct sockaddr *)&their_addr), s, sizeof s));
				printf("CLIENT: packet is %d bytes long\n", numbytes);
				buf[numbytes] = '\0';
				printf("CLIENT: packet contains \"%s\"\n", buf);

				if(buf[0]=='0' && buf[1]=='5'){//if error packet received
					fprintf(stderr, "CLIENT: got error packet: %s\n", buf);
					exit(1);
				}
				
				++block;
				if(block>MAX_PACKETS)
					block = 1;
			}
			
			fclose(fp);
		} else {//some bad packed received
			fprintf(stderr,"CLIENT ACK: expecting but got: %s\n", buf);
			exit(1);
		}
	} else { //INVALID REQUEST
		fprintf(stderr,"USAGE: tftp_c GET/PUT server filename\n");
		exit(1);
	}
	//===========MAIN IMPLEMENTATION - ENDS===========

	
	freeaddrinfo(servinfo);
	close(sockfd);
	
	return 0;
}