tftp协议（客户端和服务端）c语言实现
·
首先说结论， 看这个开源博客吧（linux下能运行）：GitCode - 开发者的代码家园
网上搜索该资料，有很多知乎或者csdn相关博客，但是很多都是复制来的，代码不全，无法运行。这里给大家推荐这个我找到的开源代码，简单又完整（其它一些开源博客，要么代码量太大太复杂，要么拆成很多个c文件，不便于理解）。此外，该协议原理解释看这个博客： TFTP是什么，一文带你了解-CSDN博客
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <errno.h>
#include <signal.h>
#include <setjmp.h>
#define DATA_SIZE 512
#define MAX_FILENAME 255
#define INITIAL_BLOCK 0
#define MAX_TIMEOUTS 5
#define TIMEOUT_SECS 3
/* Opcodes */
#define RRQ 1
#define WRQ 2
#define DATA 3
#define ACK 4
#define ERROR 5
static const char *TFTP_error_messages[] = {
"Undefined error", // Error code 0
"File not found", // 1
"Access violation", // 2
"Disk full or allocation error", // 3
"Illegal TFTP operation", // 4
"Unknown transfer ID", // 5
"File already exists", // 6
"No such user" // 7
};
extern int errno;
typedef struct {
unsigned short int opcode;
char filename[MAX_FILENAME];
char zero_0;
char mode[MAX_FILENAME];
char zero_1;
} TFTP_Request;
typedef struct {
unsigned short int opcode;
unsigned short int block;
char data[DATA_SIZE];
} TFTP_Data;
typedef struct {
unsigned short int opcode;
unsigned short int block;
} TFTP_Ack;
/* Global vars */
static int is_debugging = 0, timeout;
jmp_buf timeoutbuf, endbuf;
int get_port(char* s) {
int retval = 0;
char *a = s;
while (*a != '\0') {
if (*a >= '0' && *a <= '9') {
retval = retval * 10 + (*a - '0');
} else {
return -1;
}
a++;
}
return retval;
}
/* Returns 0 for sucess, otherwise -1. */
int make_socket(struct sockaddr_in *s, char *host, int port) {
s->sin_family = AF_INET;
if (host != NULL) {
struct hostent *he = gethostbyname(host);
if (he == NULL) {
perror("gethostbyname");
return -1;
}
s->sin_addr = *((struct in_addr *)he->h_addr);
} else {
s->sin_addr.s_addr = htonl(INADDR_ANY);
}
s->sin_port = htons(port);
memset(&(s->sin_zero), 0, 8);
return 0;
}
/* Returns 0 a file that exists, other -1. */
int file_exists(char *filename) {
struct stat filebuf;
if ( stat(filename, &filebuf) == 0 ) {
return 0;
} else {
return -1;
}
}
/* Fill in the struct using data from buffer */
void packet_to_request(TFTP_Request *r, char *buf) {
char filename[MAX_FILENAME];
char mode[MAX_FILENAME];
short signed int code;
code = *(short signed int*)buf;
buf += sizeof(r->opcode);
strcpy(filename, buf);
buf += strlen(filename) + 1;
strcpy(mode, buf);
r->opcode = ntohs(code);
strcpy(r->filename, filename);
r->zero_0 = '\0';
strcpy(r->mode, mode);
r->zero_1 = '\0';
}
/* Fill the given buffer using data from the given request */
void request_to_packet(TFTP_Request *r, char *buf) {
char *pos = buf;
*(short signed int*)pos = htons(r->opcode);
pos += sizeof(r->opcode);
strcpy(pos, r->filename);
pos += strlen(r->filename) + 1;
*pos = r->zero_0;
strcpy(pos, r->mode);
pos += strlen(r->mode) + 1;
*pos = r->zero_1;
}
/* Computes length of request */
int request_length(TFTP_Request *r) {
int len = sizeof(r->opcode) + sizeof(r->zero_0) + sizeof(r->zero_1);
len += strlen(r->filename) + 1;
len += strlen(r->mode) + 1;
return len;
}
/* Returns 0 if request has the given mode, otherwise 0 */
int request_is_mode(TFTP_Request *r, char *mode) {
if (strcmp(r->mode, mode) == 0) return 0;
return -1;
}
void request_init(TFTP_Request *r, unsigned short int opcode, char *filename, char *mode) {
memset(r, 0, sizeof(TFTP_Request));
r->opcode = opcode;
strcpy(r->filename, filename);
r->zero_0 = '\0';
strcpy(r->mode, "octet");
r->zero_1 = '\0';
}
void timer(int sig) {
switch(sig) {
case SIGALRM: {
timeout++;
if (timeout >= MAX_TIMEOUTS) {
if (is_debugging) printf("Retransmission timed out.\n");
timeout = 0;
alarm(0);
longjmp(endbuf, sig);
}
if (is_debugging) printf("Retransmitting.\n");
longjmp(timeoutbuf, sig);
} break;
case SIGINT: {
if (is_debugging) printf("Transfer interrupted.\n");
timeout = 0;
alarm(0);
longjmp(endbuf, sig);
} break;
default: break;
}
}
void send_data(int sockfd, struct sockaddr *to_addr, socklen_t addr_len, char *filename) {
int filesize, n, pos = 0, nextAck = -1;
signed short int block = 0;
int fd = open(filename, O_RDONLY, 0006);
if (fd == -1) {
perror("open");
exit(1);
}
filesize = lseek(fd, 0, SEEK_END);
lseek(fd, 0, SEEK_SET);
/* Allocate memory for DATA, ACK structs */
TFTP_Data *dataPacket;
TFTP_Ack *ack;
dataPacket = (TFTP_Data *)malloc(sizeof(TFTP_Data));
ack = (TFTP_Ack *)malloc(sizeof(TFTP_Ack));
memset(dataPacket, 0, sizeof(TFTP_Ack));
memset(ack, 0, sizeof(TFTP_Ack));
/* Read from file and send data to server */
while (pos < filesize) {
char dataBuf[DATA_SIZE] = {0};
n = read(fd, &dataBuf, DATA_SIZE);
if (n == -1) {
perror("read");
exit(1);
}
pos += n;
block++;
dataPacket->opcode = htons(DATA);
dataPacket->block = htons(block);
if (is_debugging) printf("Block #%d, %d bytes\n", block, n);
memset(dataPacket->data, 0, DATA_SIZE);
memcpy(dataPacket->data, dataBuf, n);
sigsetjmp(timeoutbuf, 1); // jump for retransmission
if (is_debugging) printf("Sending DATA for block #%d\n", block);
n = sendto(sockfd, dataPacket, 4 + n, 0, to_addr, addr_len);
if (n < 0) {
if (is_debugging) printf("Error sending DATA block #%d\n", block);
break;
}
if (sigsetjmp(endbuf, 1) != 0) {
// setup jump for retransmission timeout and interrupt
break;
}
signal(SIGINT, timer);
signal(SIGALRM, timer);
while (nextAck < 0) {
/* Receive ACK for the sent DATA */
if (is_debugging) printf("Waiting for ACK...\n");
alarm(TIMEOUT_SECS); // start new timer
n = recvfrom(sockfd, ack, sizeof(TFTP_Ack), 0, to_addr, &addr_len);
timeout = 0;
alarm(0);
if (n < 0) {
if (is_debugging) printf("Error receiving ACK for block #%d\n", block);
break;
}
if (ntohs(ack->opcode) == ERROR) {
if (is_debugging) printf("Received ERROR: %s\n", TFTP_error_messages[ntohs(ack->block)]);
}
else if (ntohs(ack->opcode) == ACK) {
/* Check block */
if (ntohs(ack->block) == block) {
nextAck = 1;
if (pos == filesize) {
if (is_debugging) printf("Received ACK for final block #%d\n", block);
break;
} else {
if (is_debugging) printf("Received ACK for block #%d\n", block);
continue;
}
} else if (ntohs(ack->block) < block) {
nextAck = -1;
}
}
}
nextAck = -1;
}
free(dataPacket);
free(ack);
close(fd);
}
void recv_data(int sockfd, char *filename) {
struct sockaddr client_addr;
int n;
socklen_t clilen;
short signed int block = 0, nextBlock = 1;
/* Allocate memory for DATA, ACK and FILE structs */
TFTP_Data *dataPacket = malloc(sizeof(TFTP_Data));
TFTP_Ack *ack = malloc(sizeof(TFTP_Ack));
memset(dataPacket, 0, sizeof(TFTP_Data));
memset(ack, 0, sizeof(TFTP_Ack));
FILE * file = fopen(filename, "ab");
while (1) {
clilen = sizeof(struct sockaddr);
int length;
if (sigsetjmp(endbuf, 1) != 0) {
// setup jump for retransmission timeout and interrupt
break;
}
signal(SIGINT, timer);
signal(SIGALRM, timer);
/* Receive the DATA */
if (is_debugging) printf("Waiting for DATA...\n");
alarm(TIMEOUT_SECS); // start new timer
n = recvfrom(sockfd, dataPacket, sizeof(TFTP_Data), 0, (struct sockaddr *)&client_addr, &clilen);
timeout = 0;
alarm(0); // void timer
if (n < 0) break;
/* Received a duplicate DATA block */
if (ntohs(dataPacket->block) < nextBlock) {
if (is_debugging) printf("Received duplicate DATA for block #%d\n", ntohs(dataPacket->block));
}
else {
length = strlen(dataPacket->data);
if (length == 0) break;
/* Fill the data buffer */
char dataBuf[DATA_SIZE+1];
strcpy(dataBuf, dataPacket->data);
if (length > DATA_SIZE) {
dataBuf[DATA_SIZE] = '\0';
length = strlen(dataBuf);
}
if (is_debugging) printf("Received DATA for block #%d of size %d\n", ntohs(dataPacket->block), length);
/* Write data to the file and check if disk is full */
fwrite(dataBuf, sizeof(char), length, file);
if (errno == ENOSPC) {
if (is_debugging) printf("Sending error: %s\n", TFTP_error_messages[3]);
ack->opcode = htons(ERROR);
ack->block = htons(3);
n = sendto(sockfd, ack, sizeof(TFTP_Ack), 0, &client_addr, clilen);
break;
}
/* Fill ACK if correct block received */
block = nextBlock;
nextBlock++;
ack->opcode = htons(ACK);
ack->block = htons(block);
}
sigsetjmp(timeoutbuf, 1); // jump for retransmission
if (is_debugging) printf("Sending ACK for block #%d\n", block);
n = sendto(sockfd, ack, sizeof(TFTP_Ack), 0, &client_addr, clilen);
if (n < 0) {
printf("Error sending ACK.\n");
break;
}
/* last block of DATA */
if (length < DATA_SIZE) break;
}
free(dataPacket);
free(ack);
fclose(file);
}
void send_error(int sockfd, struct sockaddr *to_addr, socklen_t addrlen, TFTP_Ack *ack, char *msg) {
int len = sizeof(TFTP_Ack)+strlen(msg)+1;
char *buf = (char *)malloc(len);
char *pbuf = buf;
memset(buf, 0, len);
*(short signed int*)pbuf = htons(ack->opcode);
pbuf += sizeof(ack->opcode);
*(short signed int*)pbuf = htons(ack->block);
pbuf += sizeof(ack->block);
strcpy(pbuf, msg);
sendto(sockfd, buf, len, 0, to_addr, addrlen);
free(buf);
}
int server_process(int oldsockfd, struct sockaddr *client_addr, TFTP_Request *request) {
int pid = fork();
if (pid < 0) {
perror("fork");
return -1;
}
if (pid == 0) {
close(oldsockfd);
int sockfd = 0;
if ((sockfd=socket(AF_INET,SOCK_DGRAM,0)) == -1) {
perror("socket");
exit(1);
}
struct sockaddr_in serv_addr;
make_socket(&serv_addr, NULL, 0);
if (bind(sockfd, (struct sockaddr *)&serv_addr, sizeof(struct sockaddr)) == -1) {
perror("bind");
exit(0);
}
unsigned int addr_len = sizeof(struct sockaddr);
if (getsockname(sockfd, (struct sockaddr *)&serv_addr, &addr_len) == -1) {
perror("getsockname");
exit(1);
}
if (is_debugging) printf("Child process listening on port %i\n", ntohs(serv_addr.sin_port));
/* Allocate memory for ACK struct */
TFTP_Ack *ack = (TFTP_Ack *)malloc(sizeof(TFTP_Ack));
memset(ack, 0, sizeof(TFTP_Ack));
/* Octet mode only */
if (request_is_mode(request, "octet") != 0) {
ack->opcode = htons(ERROR);
ack->block = htons(0);
send_error(sockfd, client_addr, addr_len, ack, "mode not supported");
free(ack);
close(sockfd);
free(request);
exit(1);
}
if (request->opcode == WRQ) {
/* file should not exist locally */
if ( file_exists(request->filename) == 0 ) {
exit(1);
}
/* Fill ACK struct and compute packet length */
ack->opcode = htons(ACK);
ack->block = htons(INITIAL_BLOCK);
/* Send ACK and start receiving DATA */
sendto(sockfd, ack, sizeof(TFTP_Ack), 0, client_addr, addr_len);
recv_data(sockfd, request->filename);
}
else if (request->opcode == RRQ) {
/* file must exist locally */
if ( file_exists(request->filename) == -1 ) {
exit(1);
}
/* Send data */
send_data(sockfd, client_addr, addr_len, request->filename);
}
else {
if (is_debugging) printf("Received request with unknown opcode: %i\n", request->opcode);
}
free(ack);
close(sockfd);
free(request);
exit(0);
}
return pid;
}
void chld_trap(int s) {
int pid = wait(NULL);
if (pid < 0) {
return; // wait went wrong, fly away
}
}
void run_server(int port) {
/* install signal handlers */
signal(SIGCHLD, chld_trap);
int sockfd;
struct sockaddr_in my_addr;
struct sockaddr_in client_addr;
unsigned int addr_len, numbytes;
char *buf;
/* Try to bind socket to the port */
if ((sockfd=socket(AF_INET,SOCK_DGRAM,0)) == -1) {
perror("socket");
exit(1);
}
make_socket(&my_addr, NULL, port);
if (bind(sockfd, (struct sockaddr *)&my_addr, sizeof(struct sockaddr)) == -1) {
perror("bind");
exit(1);
}
/* Listen for incoming requests until program is teminated */
if (is_debugging) printf("Listening on port %i\n", ntohs(my_addr.sin_port));
while (1) {
buf = (char *)malloc( sizeof(TFTP_Request) );
memset(buf, 0, sizeof(TFTP_Request));
addr_len = sizeof(struct sockaddr);
numbytes = recvfrom(sockfd, buf, sizeof(TFTP_Request), 0, (struct sockaddr *)&client_addr, &addr_len);
if (numbytes < 0) {
free(buf);
continue;
}
if (is_debugging) {
printf("Got packet from %s:%d, %i bytes.\n",
inet_ntoa(client_addr.sin_addr), ntohs(client_addr.sin_port), numbytes
);
}
TFTP_Request *request = (TFTP_Request *)malloc( sizeof(TFTP_Request) );
packet_to_request(request, buf);
free(buf);
server_process(sockfd, (struct sockaddr *)&client_addr, request);
free(request);
}
close(sockfd);
}
void send_request_read(char *host, int port, char *filename) {
int n, len;
int mysockfd;
struct sockaddr_in serv_addr;
struct sockaddr_in my_addr;
unsigned int addr_len;
/* Prepare the sockets */
make_socket(&serv_addr, host, port);
if ((mysockfd=socket(AF_INET,SOCK_DGRAM,0)) == -1) {
perror("socket");
exit(1);
}
make_socket(&my_addr, NULL, 0);
if (bind(mysockfd, (struct sockaddr *)&my_addr, sizeof(struct sockaddr)) == -1) {
perror("bind");
exit(1);
}
addr_len = sizeof(struct sockaddr);
/* Allocate the Ack struct */
TFTP_Ack *ack = (TFTP_Ack *)malloc(sizeof(TFTP_Ack));
memset(ack, 0, sizeof(TFTP_Ack));
/* Create the request */
TFTP_Request *request = (TFTP_Request *)malloc(sizeof(TFTP_Request));
request_init(request, RRQ, filename, "octet");
len = request_length(request);
char *req_buffer = (char*)malloc(len);
memset(req_buffer, 0, len);
request_to_packet(request, req_buffer);
/* Send the request */
sigsetjmp(timeoutbuf, 1);
if (is_debugging) printf("Sending read request to server, %i bytes.\n", len);
n = sendto(mysockfd, req_buffer, len, 0, (struct sockaddr *)&serv_addr, addr_len);
if (n < 0) {
if (is_debugging) printf("Error sending read request!\n");
free(ack);
free(request);
free(req_buffer);
close(mysockfd);
exit(1);
}
/* Just receive data */
recv_data(mysockfd, filename);
free(ack);
free(request);
free(req_buffer);
close(mysockfd);
}
void send_request_write(char *host, int port, char *filename) {
int mysockfd, n, len;
struct sockaddr_in serv_addr, my_addr;
unsigned int addr_len;
/* Prepare the sockets */
make_socket(&serv_addr, host, port);
if ((mysockfd=socket(AF_INET,SOCK_DGRAM,0)) == -1) {
perror("socket");
exit(1);
}
make_socket(&my_addr, NULL, 0);
if (bind(mysockfd, (struct sockaddr *)&my_addr, sizeof(struct sockaddr)) == -1) {
perror("bind");
exit(1);
}
addr_len = sizeof(struct sockaddr);
/* Allocate the Ack struct */
TFTP_Ack *ack = (TFTP_Ack *)malloc(sizeof(TFTP_Ack));
memset(ack, 0, sizeof(TFTP_Ack));
/* Create the request */
TFTP_Request *request = (TFTP_Request *)malloc(sizeof(TFTP_Request));
request_init(request, WRQ, filename, "octet");
len = request_length(request);
char *req_buffer = (char*)malloc(len);
memset(req_buffer, 0, len);
request_to_packet(request, req_buffer);
/* Send the request */
sigsetjmp(timeoutbuf, 1); // jump for retransmission
if (is_debugging) printf("Sending write request to server, %i bytes.\n", len);
n = sendto(mysockfd, req_buffer, len, 0, (struct sockaddr *)&serv_addr, addr_len);
if (n < 0) {
if (is_debugging) printf("Error sending write request!\n");
exit(1);
}
if (sigsetjmp(endbuf, 1) != 0) {
// jump for retransmission failure or interrupt
free(ack);
free(request);
free(req_buffer);
close(mysockfd);
exit(1);
}
/* Wait for the Ack */
if (getsockname(mysockfd, (struct sockaddr *)&my_addr, &addr_len) == -1) {
if (is_debugging) perror("getsockname");
exit(1);
}
if (is_debugging) printf("Waiting for ACK on port %d...\n", ntohs( my_addr.sin_port ));
signal(SIGINT, timer);
signal(SIGALRM, timer);
alarm(TIMEOUT_SECS);
n = recvfrom(mysockfd, ack, sizeof(TFTP_Ack), 0, (struct sockaddr *)&serv_addr, &addr_len);
alarm(0);
timeout = 0;
if (n < 0) {
if (is_debugging) printf("Error receiving ACK from server!\n");
exit(1);
}
/* Check the Opcode */
if (ntohs(ack->opcode) == ERROR) {
if (is_debugging) printf("Received ERROR: %s\n", TFTP_error_messages[ntohs(ack->block)]);
}
else if ( ntohs(ack->opcode) == ACK && ntohs(ack->block) == INITIAL_BLOCK ) {
if (is_debugging) printf("Received ACK for block #%d\n", ntohs(ack->block));
send_data(mysockfd, (struct sockaddr *)&serv_addr, addr_len, filename);
} else {
if (is_debugging) printf("Received packet other than expected ACK\n");
}
free(ack);
free(request);
free(req_buffer);
close(mysockfd);
}
void run_client(char *host, int port, char mode, char *filename) {
void (* sender)(char *, int , char *) = NULL;
int exist = (mode == 'r') ? 0 : -1;
if (file_exists(filename) == exist) {
/* Nothing to do here */
exit(1);
}
sender = (mode == 'r') ? &send_request_read : &send_request_write;
if (sender != NULL) sender(host, port, filename);
}
/*
* Server: mytftp -l [-p port] [-v]
* Client: mytftp [-p port] [-v] [-r|w file] host
*/
int main(int argc, char** argv) {
int server = 0;
int port = 3335;
char mode = 0;
char *filename = NULL;
char *host = NULL;
/* Parse the arguments */
while (--argc > 0) {
char *str = *++argv;
if (*str != '-') {
host = (char *)malloc( sizeof(char)*(strlen(str)+1) );
strcpy(host, str);
continue;
}
str++;
if (*str == 'l') {
server = 1;
}
else if (*str == 'p') {
if (--argc > 0) {
port = get_port(*++argv);
if (port < 0) {
printf("Invalid port number: %s\n", *argv);
exit(0);
}
}
}
else if (*str == 'v') {
is_debugging = 1;
printf("Verbose mode on.\n");
}
else if (*str == 'r' || *str == 'w') {
mode = *str;
--argc;
filename = (char *)malloc( sizeof(char)*(strlen(*++argv)+1) );
strcpy(filename, *argv);
}
}
if (server == 1) {
run_server(port);
} else {
if (host != NULL && mode > 0 && filename != NULL) {
run_client(host, port, mode, filename);
free(host);
free(filename);
} else {
printf("Usage:\nServer: mytftp -l [-p port] [-v]\nClient: mytftp [-p port] [-v] [-r|w file] host\n");
}
}
return 0;
}
更多推荐
2
0- 0
已为社区贡献23条内容
所有评论(0)