server.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
#define MINIBUF 512
#define server_port 4009

int getSocket(int* port){
	int ret;		
	register int socketfd;		// server 描述符 
	struct sockaddr_in local;	// 本地地址
	
	if ((socketfd = socket(AF_INET, SOCK_STREAM, 0)) < 0){
		fprintf(stderr, "fail to initial socket!\n");
		exit(1);
	}
	local.sin_family = AF_INET;
	local.sin_addr.s_addr = INADDR_ANY;
	local.sin_port = htons(*port);

	if ((ret = bind(socketfd, (struct sockaddr *)&local, sizeof(local))) == -1){
		fprintf(stderr, "Bind unseccessfully!\n");
		exit(2);
	}
	int len = sizeof(local);
	getsockname(socketfd,(struct sockaddr*)&local, &len);
	*port = ntohs(local.sin_port);
	return socketfd;
}

void contact(int clientSocketfd, int number){
	char buf[BUFF];
	int dataSockfd;
	char file[BUFF];
	int rs,src,target,k;
	
	char root[BUFF];
	FILE* fp=popen("pwd","r");
	fgets(root,BUFF,fp);
	pclose(fp);
	
	while(1){
		if(read(clientSocketfd,buf,BUFF)>0){
			printf("The command from the clientd%d is %s\n", number, buf);
			//printf("!!%c!!%c!!%c!!\n", buf[0],buf[1],buf[2]);
		}
		if(buf[0] == 'Q' && buf[1] == 'U' && buf[2] == 'I' && buf[3] == 'T'){
			printf("The client %d quits", number);
			return;
		}
		else if (buf[0] == 'P' && buf[1] == 'W' && buf[2] == 'D'){
			FILE* fp=popen("pwd","r");
			if((fgets(file,BUFF,fp)) != NULL){
				printf("Current directory is : %s", file);
				write(clientSocketfd, (char *)(file), BUFF);
			}
			pclose(fp);
		}
		else if (buf[0] == 'D' && buf[1] == 'I' && buf[2] == 'R'){
			FILE * pf=popen("ls","r");
			while(fgets(file,BUFF,pf) != NULL){
				write(clientSocketfd,file,BUFF);
			}
			pclose(pf);
			write(clientSocketfd,"\n",BUFF);
		}
		else if (buf[0] == 'C' && buf[1] == 'D' && buf[2] == 'U' && buf[3] == 'P'){
			FILE* fp=popen("pwd","r");
			if((fgets(file,BUFF,fp)) != NULL){
				if (strcmp(file, root) == 0){
					printf("can't access father dir!\n");
					write(clientSocketfd,"\n",BUFF);
					continue;
				}
				int i;
				for (i = 0; file[i] != '\0'; i++){}
				for (; file[i] != '/'; i--){}
				file[i] = '\0';
			}
			pclose(fp);
			rs = chdir(file);
			if(rs == 0){
				FILE* fp=popen("pwd","r");
				if((fgets(file,BUFF,fp)) != NULL){
					printf("Current directory is : %s", file);
					write(clientSocketfd,(char *)(file),BUFF);
				}
				pclose(fp);
			}
			else{
				write(clientSocketfd,"\n",BUFF);
			}
		}
		
		else if (buf[0] == 'C' && buf[1] == 'D'){
			rs = chdir((char*)(buf+3));
			if(rs== 0){
				FILE* fp=popen("pwd","r");
				if((fgets(file,BUFF,fp)) != NULL){
					printf("Current directory is : %s", file);
					write(clientSocketfd,(char *)(file),BUFF);
				}
				pclose(fp);
			}
			else{
				write(clientSocketfd,"\n",BUFF);
			}
		}
		else if(buf[0] == 'G' && buf[1] == 'E' && buf[2] == 'T'){
			printf("Loading starts!\n");
			strcpy(file, (char *)(buf+4));
			if((src = open(file,O_RDONLY))<0){
				printf("file %s is not exist!\n", file);
				write(clientSocketfd,"ERROR",BUFF);
			}
			else{
				int port = 0;
				dataSockfd = getSocket(&port);
				listen(dataSockfd, 20);
				sprintf(buf, "%d", port);
				write(clientSocketfd, buf, BUFF);	// send "<dataSocketPort>"
				read(clientSocketfd, buf, BUFF);	// receive "READY" or "ERROR"
				//printf("here %s\n",buf);
				if (buf[0] == 'E'){
					close(src);
					close(dataSockfd);
					continue;
				}
				struct sockaddr_in client_in;		// client address
				// accept
				int len = sizeof(struct sockaddr_in);
				int csk;
				if ((csk = accept(dataSockfd, 
					(struct sockaddr *)&client_in, &len)) == -1){
					printf("accept error\n");
				}
				lseek(src, 0, SEEK_SET);
				memset(buf, 0x0 ,BUFF);
				while((k = read(src,buf,BUFF)) > 0){			
					write(csk, buf, k);
				}
				write(csk, 0, 0);
			}
			close(src);
			close(dataSockfd);
			printf("Loading finishes\n");
		}
		
		else if(buf[0] == 'P' && buf[1] == 'U'&& buf[2] == 'T')
		{
			strcpy(file, (char *)(buf+4));
			FILE * res=popen("ls","r");
			int isExist = 0;
			while(fgets(buf,BUFF,res) != NULL){
				int i;
				for (i = 0; buf[i] != '\n'; i++){}
				buf[i] = '\0';
				if (strcmp(buf, file) == 0){
					printf("File %s has already existed!\n", file);
					write(clientSocketfd, "ERROR", BUFF);	// send "ERROR"
					isExist = 1;
					break;
				}
			}
			if (isExist == 1)
				continue;
			pclose(res);
			
			if((target = open(file, O_WRONLY|O_CREAT|O_TRUNC, 0644)) < 0){
				printf("error to write to file %s!\n", file);
				write(clientSocketfd, "ERROR", BUFF);	// send "ERROR"
				continue;
			}
			else{
				int port = 0;
				dataSockfd = getSocket(&port);
				listen(dataSockfd, 20);
				sprintf(buf, "%d", port);
				write(clientSocketfd, buf, BUFF);	// send "<dataSocketPort>"
				
				struct sockaddr_in client_in;		// client address
				// accept
				int len = sizeof(struct sockaddr_in);
				int csk;
				if ((csk = accept(dataSockfd, (struct sockaddr *)&client_in, &len)) == -1){
					printf("accept error\n");
				}
				while ((k = read(csk, buf, BUFF)) > 0){
					write(target, buf, k);
					if (k != BUFF)
						break;
				}
			}
			close(target);
			close(dataSockfd);
			printf("Puting has finished\n");
		}
		
		
	}

}

int main(int argc, char *argv[]){
	char command[MINIBUF];		// 接收的命令
	
	int clientNum = 0;		// client数
	int ret;			
	int socketfd;			// server socket描述符
	int clientSocketfd;		// client socket描述符
	char buf[BUFF];                  //
	int port = server_port;
	socketfd = getSocket(&port);
	
	// listen
	listen(socketfd, 20);
	while (1){
		struct sockaddr_in client_in;		// client address
		int len = sizeof(struct sockaddr_in);
		if ((clientSocketfd = accept(socketfd, (struct sockaddr *)&client_in, &len)) == -1){
			printf("accept error\n");
		}
	
		clientNum++;
		sprintf(buf, "%d", clientNum);
		printf("Client %s is connected\n", buf);
		printf("Client name: %s\n", inet_ntoa(client_in.sin_addr));
		
		int pid;                   //多线程
		switch (pid = fork()){
		case 0:
			close(socketfd);
			write(clientSocketfd, buf, BUFF);  //tell the client which number it is 
			contact(clientSocketfd, clientNum);
			close(clientSocketfd);
			exit(1);
		case -1:
			printf("fork error\n");
			break;
		default:
			close(clientSocketfd);
			break;
		}
	}
	return 0;
}