client.c

在Linux系统上使用Socket接口实现FTP客户端和服务器的程序

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/fcntl.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <errno.h>
#include <string.h>
#include <arpa/inet.h>


#define BUFF 1024

void dispatch(char *cmd, int sockfd);

int getSocket(char *address, int port)
{
	int ret;
	register int socketfd;
	struct sockaddr_in sin;
	
	if ((socketfd = socket(AF_INET, SOCK_STREAM, 0)) < 0){
		fprintf(stderr, "fail to initial socket!\n");
		exit(1);
	}
	
	sin.sin_family = AF_INET;
	sin.sin_port = htons(port);
	
	inet_pton(AF_INET, address, &sin.sin_addr);
	printf("Server address: %s\n",inet_ntoa(sin.sin_addr));
	printf("Server port: %d\n",ntohs(sin.sin_port));
	
	int len = sizeof(sin);
	if ((ret = connect(socketfd, (struct sockaddr *)&sin, len)) == -1){
		fprintf(stderr, "can't connect server!\n");
		exit(2);
	}
	
	return socketfd;
}



void contact(int sockfd)
{
	char cmd[BUFF];
	memset(cmd, 0, BUFF);
	while (1){
		printf("ftp>:");
		fgets(cmd,BUFF,stdin);
		dispatch(cmd, sockfd);
	}
}

char * isCdCmd(char *cmd)
{	
	char *temp = cmd;
	while (*temp == '\t' || *temp == ' ')
		temp++;
	if (*temp == 'c' && *(temp+1) == 'd'){
		temp += 2;
		while (*temp == '\t' || *temp == ' ')
			temp++;
	}
	else{
		return 0;
	}
	int i;
	if (*temp == '\n'){
		printf("Usage: cd <subdirectory>\n");
		return (void *)(-1);
	}
	for (i = 0; *(temp+i) != '\0'; i++){
		if (*(temp+i) == ' ' || *(temp+i) == '\t'){
			printf("Usage: cd <subdirectory>\n");
			return (void *)(-1);
		}
		if (*(temp+i) == '\n')
			*(temp+i) = '\0';
	}
	if (*temp == '.' && *(temp+1) == '.')
		return (void *)1;
	return temp;
}

char * isGetCmd(char *cmd){	
	char *temp = cmd;
	while (*temp == '\t' || *temp == ' ')
		temp++;
	if (*temp == 'g' && *(temp+1) == 'e' && *(temp+2) == 't'){
		temp += 3;
		while (*temp == '\t' || *temp == ' ')
			temp++;
	}
	else{
		return 0;
	}
	int i;
	if (*temp == '\n'){
		printf("Usage: get <fileName>\n");
		return (void *)(-1);
	}
	for (i = 0; *(temp+i) != '\0'; i++){
		if (*(temp+i) == ' ' || *(temp+i) == '\t'){
			printf("Usage: get <fileName>\n");
			return (void *)(-1);
		}
		if (*(temp+i) == '\n')
			*(temp+i) = '\0';
	}
	return temp;
}

char * isPutCmd(char *cmd){	
	char *temp = cmd;
	while (*temp == '\t' || *temp == ' ')
		temp++;
	if (*temp == 'p' && *(temp+1) == 'u' && *(temp+2) == 't'){
		temp += 3;
		while (*temp == '\t' || *temp == ' ')
			temp++;
	}
	else
	{
		return 0;
	}
	int i;
	if (*temp == '\n')
	{
		printf("Usage: put <fileName>\n");
		return (void *)(-1);
	}
	for (i = 0; *(temp+i) != '\0'; i++)
	{
		if (*(temp+i) == ' ' || *(temp+i) == '\t')
		{
			printf("Usage: put <fileName>\n");
			return (void *)(-1);
		}
		if (*(temp+i) == '\n')
			*(temp+i) = '\0';
	}
	return temp;
}

void quitCmd(int sockfd){
	write(sockfd, "QUIT", BUFF);
	close(sockfd);
	printf("Goodbye!! Welcome to use this again!\n");
	exit(0);
}

void pwdCmd(int sockfd){
	write(sockfd, "PWD", BUFF);
	char buf[BUFF] = {0};
	read(sockfd, buf, BUFF);
	if (*buf == '\0')
		strcpy(buf, "\n");
	printf("Current server directory is %s", buf);
}

void dirCmd(int sockfd){
	write(sockfd, "DIR", BUFF);
	char buf[BUFF] = {0};
	
	while (read(sockfd, buf, BUFF) > 0){
		if (buf[0] == '\n')
			break;
		printf("\t%s", buf);
	}
}

void cdCmd(char *file, int sockfd){
	char buf[BUFF] = "CD ";
	int i;
	for (i = 0; file[i] != '\0'; i++)
	{
		buf[i+3] = file[i];
	}
	buf[i+3] = '\0';
	
	write(sockfd, buf, BUFF);	// send "CD <dir>"
	read(sockfd, buf, BUFF);	// receive "<dir>"
	if (*buf == '\n')
	{
		printf("fail to change directory\n");
	}
	else
	{
		if (*buf == '\0')
			strcpy(buf, "\n");
		printf("Current server directory is ./%s", buf);
	}
}

void cdupCmd(int sockfd)
{
	char buf[BUFF] = {0};
	write(sockfd, "CDUP", BUFF);	// send "CDUP"
	read(sockfd, buf, BUFF);	// receive "<dir>"
	if (*buf == '\n'){
		printf("fail to change directory\n");
	}
	else{
		if (*buf == '\0')
			strcpy(buf, "\n");
		printf("Current server directory is ./%s", buf);
	}
}

void getCmd(char *file, int sockfd)
{
	printf("try to get file:%s\n", file);
	
	char buf[BUFF] = "GET ";
	int i;
	for (i = 0; file[i] != '\0'; i++){
		buf[i+4] = file[i];
	}
	buf[i+4] = '\0';
	
	write(sockfd, buf, BUFF);	// send "GET <file>"
	read(sockfd, buf, BUFF);	// receive "<dataSocketPort>" or "ERROR"
	if (*buf == 'E'){
		printf("file %s is not exist!\n", file);
		return;
	}
	
	int target;
	if((target = open(file, O_WRONLY|O_CREAT|O_TRUNC, 0644)) < 0){
		printf("error to write to file %s!\n", file);
		write(sockfd, "ERROR", BUFF);	// send "ERROR"
		return;
	}
	else
		write(sockfd, "READY", BUFF);	// send "READY"
	
	struct sockaddr_in server;
	int len = sizeof(server);
	getsockname(sockfd,(struct sockaddr*)&server, &len);
	register int dataSk = getSocket(inet_ntoa(server.sin_addr), atoi(buf));
	
	int k;
	printf("downloading...\n");
	while ((k = read(dataSk, buf, BUFF)) > 0){
		write(target, buf, k);
		if (k != BUFF)
			break;
	}
	close(dataSk);
	close(target);
	printf("finished!\n");
}

void putCmd(char *file, int sockfd)
{
	printf("try to upload file:%s\n", file);
	int source;
	if((source = open(file,O_RDONLY)) < 0)
	{
		printf("fail to open file %s!\n", file);
		return;
	}
		
	char buf[BUFF] = "PUT ";
	int i;
	for (i = 0; file[i] != '\0'; i++)
	{
		buf[i+4] = file[i];
	}
	buf[i+4] = '\0';
	
	write(sockfd, buf, BUFF);	
	read(sockfd, buf, BUFF);	// receive "<dataSocketPort>" or "ERROR"
	if (*buf == 'E')
	{
		printf("file %s is already exist in server!\n", file);
		close(source);
		return;
	}
	
	struct sockaddr_in server;
	int len = sizeof(server);
	getsockname(sockfd,(struct sockaddr*)&server, &len);
	register int dataSk = getSocket(inet_ntoa(server.sin_addr), atoi(buf));
	
	int k;
	printf("uploading...\n");
	lseek(source, 0, SEEK_SET);
	memset(buf, 0x0 ,BUFF);
	while((k = read(source,buf,BUFF)) > 0)
	{			
		write(dataSk, buf, k);
	}
	write(dataSk, 0, 0);
	
	close(dataSk);
	close(source);
	printf("finished!\n");
}

void helpCmd(){
	printf("?\n\tdisplay help message\n");
	printf("!dir\n\tlist the client's current directory\n");
	printf("get\n\tfetch a file from server\n\tget <filename>\n");
	printf("put\n\tunload a file to server\n\tput <filename>\n");
	printf("pwd\n\tdisplay current directory of server\n");
	printf("dir\n\tlist  files in current directory of server\n");
	printf("cd\n\tchange current directory of server\n\tcd <subdirectory>|\"..\"\n");
	printf("quit\n\tquit ftp client\n");
}

void lowerCase(char *cmd){
	int i;
	while (*cmd == '\t' || *cmd == ' ')
		cmd++;
	
	for (i = 0; cmd[i] != ' '; i++){
		if (cmd[i] >= 'A' && cmd[i] <= 'Z')
			cmd[i] += ('a'-'A');
	}
}

void dispatch(char *cmd, int sockfd){
	char *file;
	int r;
	lowerCase(cmd);
	while (*cmd == '\t' || *cmd == ' ')
		cmd++;
		
	if (*cmd == '?'){
		helpCmd();
		return;
	}
	
	if (*cmd == '!'){
		if(*(cmd+1) == 'd' && *(cmd+2) == 'i' &&  *(cmd+3) == 'r'){
			char buf[BUFF];
			FILE * pf=popen("ls","r");
			while(fgets(buf,BUFF,pf) != NULL){
				printf("\t%s",buf);
			}
			pclose(pf);
			printf("\n");
			return;
		}
			
	}
	
	else if (*cmd == 'q'){
		char * temp = cmd;
		if (*temp == 'q' && *(temp+1) == 'u' && *(temp+2) == 'i' && *(temp+3) == 't'){
			temp += 4;
			while (*temp == '\t' || *temp == ' ')
				temp++;
			if(*temp == '\n')
				quitCmd(sockfd);
			else 
				return;
		}
		else 
			return;
	}
	
	else if (*cmd == 'p'){
		char *temp = cmd;
		if (*temp == 'p' && *(temp+1) == 'w' && *(temp+2) == 'd'){
			temp += 3;
			while (*temp == '\t' || *temp == ' ')
				temp++;
			if(*temp == '\n')
				pwdCmd(sockfd);
			return;
		}
		else if((file = isPutCmd(cmd)) != 0){
			if ((int)file == -1)
				return;
			else
				putCmd(file, sockfd);
			return;
		}
		else return;
		
	}
	
	else if (*cmd == 'd'){
		char *temp = cmd;
		if (*temp == 'd' && *(temp+1) == 'i' && *(temp+2) == 'r'){
			temp += 3;
			while (*temp == '\t' || *temp == ' ')
				temp++;
			if(*temp == '\n')
				dirCmd(sockfd);
		}
		return;
	}
	
	else if (*cmd == 'c'){
		if ((file = isCdCmd(cmd)) != 0){
			if ((int)file == -1)
				return;
			else if ((int)file == 1)
				cdupCmd(sockfd);
			else
				cdCmd(file, sockfd);
			return;
		}
		else return;
	}
	
	else if(*cmd == 'g'){
		if((file = isGetCmd(cmd)) != 0){
			if ((int)file == -1)
				return;
			else
				getCmd(file, sockfd);
			return;
		}
	}
	
	printf("Unknown ftp command!\n");
	return;
}


int main(int argc, char *argv[])
{
	if (argc != 3){
		printf("Usage:client <address> <port>\n");
		return 0;
	}
	
	int target,ret;
	char buf[BUFF];
	register int socketfd = getSocket(argv[1], atoi(argv[2]));
	
	if(read(socketfd,buf,BUFF) > 0){
		printf("You are Client %s\n",buf);
	}
	
	contact(socketfd);
	return 0;
}