TIP: Simple FTP server interaction
NOTE: THis post contains code that uses nonstandard classes from the sun.net hierarchies. It is not guaranteed that the required classes will be present on all, or any Java2 distribution, or that behaviour will be consistent across deployments of the J2SDK
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Intro:
While looking for a simple way to interact with an ftp server (i wasnt shifting hundreds of files) and not really wanting to write my own client I considered writing an extension to the URLConnection class, as HttpURLConnection exists, but Ftp apparently does not. (i also considered writing FTPFile and mimicking File for most things.. I may still)
Anyways, i dscovered that FtpURLCOnnection DOES exist, but it is not standard, probably because the darn thing is so hard to ratify.
I played with ti a while and decided to post this as a FYI for the community BUT ALSO TO RECEIVE SOME FEEDBACK from users who have maybe used this before, or have some ideas I have not tried.
code:
the following code snippet reads a file from an ftp server, and dumps it to the console (hint: try it with a SMALL binary or ascii file)
Code:
import java.net.*;
import java.io.InputStream;
public class FTPRead{
public static void main(String[] argv)throws Exception{
URL u = new URL("ftp://USER:PASS@HOST:PORT/PATH/TO/THEFILE");
URLConnection uc = u.openConnection() ;
uc.setDoInput(true);
InputStream in = uc.getInputStream() ;
byte[] buf = new byte[4096];
for(int br = in.read(buf); br > -1; br = in.read(buf)){
System.out.write(buf, 0 , br);
}
in.close();
}
}
it appears that the user/pass needs embedding in the URL; i know of no way to pass it, as the classes in use are nonstandard, and i do not know if they use the Properties at all.
There is virtually nothing you can do to protect this password either, if your source files are stolen.. So take care with this..
Some code to read a DIRECTORY
Code:
import java.net.*;
import java.io.InputStream;
public class FTPRead{
public static void main(String[] argv)throws Exception{
URL u = new URL("ftp://USER:PASS@HOST:PORT/PATH/TO/THE/DIR/");
URLConnection uc = u.openConnection() ;
uc.setDoInput(true);
InputStream in = uc.getInputStream() ;
byte[] buf = new byte[4096];
for(int br = in.read(buf); br > -1; br = in.read(buf)){
System.out.write(buf, 0 , br);
}
in.close();
}
}
it appears that, if the url has a trailing slash, a directory is assumed, and a listing is provided in the following format:
-rwxrwxrwx 1 owner group 69414 Jan 15 6:01 030107cnd.exe
rwxrwxrwx = permissions for local user (first rwx), group (2nd rwx) and everyone else (third rwx)
when writing files, i have no iodea how to change these
any client you write should parse this output and decide what group of people it belongs to
the following code writes a file to the server:
Code:
import java.net.*;
import java.io.OutputStream;
public class FTPTest{
public static void main(String[] argv)throws Exception{
URL u = new URL("ftp://USER:PASS@HOST:PORT/PA/TH/TO/FI/LE/THEFILE") ;
URLConnection uc = u.openConnection() ;
uc.setDoOutput(true);
OutputStream out = uc.getOutputStream() ;
out.write("THIS DATA WILL BE WRITTEN TO FILE".getBytes());
out.close();
}
}
--
Now, can anyone tell me how comphehensive the FtpURLConnection is? does it default to binary transfer mode, 777 permissions, username and pass another way etc.. ?
Re: TIP: Simple FTP server interaction
Code:
import java.net.*;
import java.io.OutputStream;
public class FTPTest{
public static void main(String[] argv)throws Exception{
URL u = new URL("ftp://USER:PASS@HOST:PORT/PA/TH/TO/FI/LE/THEFILE") ;
URLConnection uc = u.openConnection() ;
uc.setDoOutput(true);
OutputStream out = connect.getOutputStream() ;
out.write("THIS DATA WILL BE WRITTEN TO FILE".getBytes());
out.close();
}
}
okay when i go to compile this peice of code i get an varible error with connect.getOutputStream(); i dont think that connect is spossed to be a user diffend var, so can you explane
Re: TIP: Simple FTP server interaction
You did not define connect anywhere in your program. Perhaps you mean:
Code:
OutputStream out = uc.getOutputStream()
?
Re: TIP: Simple FTP server interaction
Re: TIP: Simple FTP server interaction
my apol.. looks like i left a varaible name in there from the "unfriendly" version of the code..
Re: TIP: Simple FTP server interaction
okay i have been using the ftp programes above in a applaction verision. But now when i try and use them in an applet i get java.security.AccessControlException: access denied
does any one know what i can do to stop this from happening
Alir
Re: TIP: Simple FTP server interaction
applets may only connect to the server that served them. this means if your website is www.alirblack.com and youre attempting to connect to ftp.microsoft.com, youll get an acces denied error
several solutions:
run your webserver and ftp server on teh same machine (easiest)
run a proxy on the webserver to the real ftp server (harder)
dont use an applet (always a good idea; applets are retarded)
allow the security restriction (hard. dont ask me about it.. start a new thread if you want an answer)
Re: TIP: Simple FTP server interaction
thanks man, i guess i have to make a choice then right?
Re: TIP: Simple FTP server interaction
hI,
I am interested in sending a file from a user's PC to a server. i wanted to know if I can edit the code where you send the string data to read some data from a text file and send that data to a specific file on the webserver. Can you help me ? I amnew to Java ..also is it possible to get a fiel form a user's PC in a servlet?
thanks,
anonsu
Re: TIP: Simple FTP server interaction
Quote:
Originally Posted by anonsu
hI,
I am interested in sending a file from a user's PC to a server. i wanted to know if I can edit the code where you send the string data to read some data from a text file and send that data to a specific file on the webserver. Can you help me ?
the following code reads from a file:
Code:
FileInputStream fis = new FileInputStream("C:\testfile.exe");
byte[] buffer = new byte[4096];
for(int bytesRead = fis.read(buffer); bytesRead > -1; bytesRead = fis.read(buffer){
//the buffer contains up to 4096 bytes of data from the file
<some output destination>.write(buffer, 0, bytesRead);
}
fis.close();
what destination you write to is up to you.. to write the bytes to the server, you would write them to the 'out' output stream
Quote:
I amnew to Java ..also is it possible to get a fiel form a user's PC in a servlet?
thanks,
anonsu
no. servlets cannot get files from user PCs, but they can receive them if the user sends them. While you may not see a difference, there is a defined and clear one in terms of client and server roles.
Re: TIP: Simple FTP server interaction
Hi
I need to write 2 files to 2 different directories in my ftp server,
but the path to the destination file is already predefined in the
URL - PA/TH/TO/FI/LE/THEFILE
URL u = new URL("ftp://USER:PASS@HOST:PORT/PA/TH/TO/FI/LE/THEFILE") ;
How can i change the destination directories dynamically?
Your help will beappreciated
1 Attachment(s)
Re: TIP: Simple FTP server interaction
I have this class for FTP (see attached FTP.java) that you can use to open a connection to a server and send commands, as with an FTP client.
For instance, use it in a program like this:
Code:
...
// start the FTP session; host is the remote server name
FTP ftp = new FTP(host);
// login
ftp.user(ftpUsr, ftpPwd);
// change to binary mode
ftp.binary();
// write a file to the remote server
ftp.put(localFile, remoteFile);
// change to another folder in the server
ftp.cd(remoteDir);
// write several files (localFiles may have wildcards)
ftp.mput(localFiles);
// close the connection
ftp.logout();
...
