基于主动模式的ftp客户端

 #include<stdio.h>
 #include<sys/socket.h>
 #include<stdlib.h>
 #include<string.h>
 #include<strings.h>
 #include<unistd.h>
 #include<netinet/in.h>
 #include<netdb.h>
 #include<errno.h>
 #include<sys/types.h>
 #include<sys/stat.h>
 #include<fcntl.h>
 #define SERV_PORT 21
 #define MAXSIZE 1024
 #define SA struct sockaddr
 static int control_sockfd;
 int npsupport;
 int login_yes;
 int f;//f=0时为默认文件结构
int login();
 void ftp_list(int control_sockfd);
 void zeromery(char *a,int len);
 void ftp_pwd(int control_sockfd);
 void ftp_changdir(char dir[],int control_sockfd);
 void ftp_quit(int control_sockfd);
 void ftp_creat_mkd(char *path,int control_sockfd);
 void ftp_back(int control_sockfd);
 void ftp_stru(int control_sockfd);
 void ftp_rest(int control_sockfd);
 int ftp_download(int control_sockfd);

 char *itoa(int value, char *string, int radix);
 int  main(int argc,char **argv)
 {
     printf("ftp>");
     char command[MAXSIZE];
     char*cmd;
     scanf("%s",command);
     cmd=command;
     while(*(cmd)==' ')
         cmd++;

     if(strncmp(cmd,"login",5)==0)
     {
         login();
         if(login_yes==1)
         {
             while(1)
             {
             comm:            
                 sleep(1);
                 printf("ftp>");
                 zeromery(command,1024);
                 scanf("%s",command);
                 cmd=command;
                 while(*(cmd)==' ')
                 cmd++;
                 if(strncmp(cmd,"pasv",4)==0)
                 {
                     ftp_list(control_sockfd);
                 }