ftpclient.c

I managed to act as an FTP client in C just using sockets... Its really not too bad.

Now of course the client I made wasn't compatible with ALL ftp servers I am quite sure, I just needed to get it to connect to a solaris box. But it did work testing on some windows ftp server...

remember to wait for the server to send you ALL of the data it needs to, before your client starts spitting commands at it. Take a look at the return code numbers it sends you also. And one very important thing... Be sure to strcat(ftp_cmd,"\r\n"); before you send it, those are the termination characters...

Code:

int ftpRecvResponse(int sock, char * buf) {
   int i;

   if (recv(sock, buf, 5120, 0) == -1) {//receive the data
      perror("recv");
      return 0;;
   }
   for(i=(strlen(buf) - 1);i>0;i--) {
      if(buf[i]=='.' || buf[i]=='\r') { 
         buf[i+1]='\0';
         break;
      }
   }
   printf("%s\n",buf); //print response to the screen
   return 0;
}

int ftpNewCmd(int sock, char * buf, char * cmd, char * param) {
   strcpy(buf,cmd);
   if(strlen(param) > 0) {
      strcat(buf," ");
      strcat(buf,param);
   }
   strcat(buf,"\r\n");
   printf("*%s",buf); //print the cmd to the screen
   if(send(sock, buf, strlen(buf), 0) == -1) {
      perror("send");
      return 0;
   }
   //clear the buffer
   return 0;
}

int ftpConvertAddy(char * buf, char * hostname, int * port) {
   unsigned int i,t=0;
   int flag=0,decCtr=0,tport1,tport2;
   char tmpPort[6];
   //example data in quotes below:
   //"227 Listening on (149,122,52,162,4,20)"
   //4 * 256 + 20 = 1044
   for(i=0;i3)
         hostname[i]='\0';
   }
   return 0;
}

int ftpSendFile(char * buf, char * host, int port) {
   int sd;
   struct sockaddr_in pin;
   struct hostent *hp;

   if ((hp = gethostbyname(host)) == 0) {
      perror("gethostbyname");
      return -1;
   }
   memset(&pin, 0, sizeof(pin));
   pin.sin_family = AF_INET;
   pin.sin_addr.s_addr = ((struct in_addr *)(hp->h_addr))->s_addr;
   pin.sin_port = htons(port);
   if ((sd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
      perror("socket");
      return -1;
   }
   if (connect(sd,(struct sockaddr *)  &pin, sizeof(pin)) == -1) {
      perror("connect");
      return -1;
   }
   if(send(sd, buf, strlen(buf), 0) == -1) {
      perror("send");
      return -1;
   }
   closesocket(sd); //close the socket
   return 0;
}

int ftpProcess(char *hostname, char *username, char *password, char *file, char *filename, char *path) {
   int sd;
   struct sockaddr_in pin;
   struct hostent *hp;
   char tmpHost[100];
   int tmpPort;
   char buf[5120];

   if ((hp = gethostbyname(hostname)) == 0) {
      perror("gethostbyname");
      return -1;
   }

   memset(&pin, 0, sizeof(pin));
   pin.sin_family = AF_INET;
   pin.sin_addr.s_addr = ((struct in_addr *)(hp->h_addr))->s_addr;
   pin.sin_port = htons(FTPPORT);

   if ((sd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
      perror("socket");
      return -1;
   }
   if (connect(sd,(struct sockaddr *)  &pin, sizeof(pin)) == -1) {
      perror("connect");
      return -1;
   }
   if(ftpRecvResponse(sd,buf)==1) {  //wait for ftp server to start talking
    if(strncmp(buf,"220",3)==0) {  //make sure it ends with a 220
     if(ftpNewCmd(sd,buf,"USER",username)==1) {  //issue the command to login
      if(ftpRecvResponse(sd,buf)==1) {  //wait for response
       if(strncmp(buf,"331",3)==0) {  //make sure response is a 331
        if(ftpNewCmd(sd,buf,"PASS",password)==1) {  //send your password
         if(ftpRecvResponse(sd,buf)==1) { //wait for response
          if(strncmp(buf,"230",3)==0) { //make sure its a 230
           if(ftpNewCmd(sd,buf,"PASV","")==1) {  //notify server we want to pass a file
            if(ftpRecvResponse(sd,buf)==1) {  //wait for response
             if(strncmp(buf,"227",3)==0) {  //make sure it starts with a 227
              ftpConvertAddy(buf,tmpHost,&tmpPort); //then convert the return to usable data
              if(ftpNewCmd(sd,buf,"STOR",filename)==1) {  //set the file name AND
               ftpSendFile(file,tmpHost,tmpPort);
               if(ftpRecvResponse(sd,buf)==1) {        //wait for a response
                if(strncmp(buf,"150",3)==0) {  //make sure its a 150 so we know the server got it all
                 if(ftpRecvResponse(sd,buf)==1) {
                  if(strncmp(buf,"226",3)==0) {
                  .......
//close all if()s or do it some better way, close the socket when done.

i know its not the prettiest, but it works quite well. I plan on cleaning it up and making an example to throw out there for those who don't like 3rd party libraries...

PM or email me if you need anything else.

---

Last edited by mschoolbus : September 18th, 2003 at 03:08 PM.