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From "Oscar Usifer" <oscaru...@programmer.net>
Subject [commons-net] How to add timeouts to FTP client connections?
Date Mon, 23 Jul 2007 23:41:43 GMT
Folks,

I am writing an ftp client that uploads a file to more than one (many) ftp servers simultaneously.
I want to add some fault tolerance so that if one server goes offline during the transfer,
the upload is completed to the running servers. I've tried to capture this situation by blocking
packets (via iptables) on one ftp server, and seeing if it triggers a timeout condition/exception
(from setting setSoTimeout) in the ftp client, but unfortuantley the connection only hangs.
Note I am using rwinston's commons-net-ftp-2.0.0-SNAPSHOT.jar. The code below is a command
line example of the ftp client. Any suggestions?

Thanks,
OSC

import java.io.OutputStream;
import org.apache.commons.net.ftp.FTPClient;
public class FTPServer {
   boolean online = true;
   FTPClient client = null;
   String hostname = null;
   OutputStream os = null;
}

import java.io.FileInputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.Random;

import org.apache.commons.net.PrintCommandListener;
import org.apache.commons.net.ftp.FTP;
import org.apache.commons.net.ftp.FTPClient;
import org.apache.commons.net.ftp.FTPConnectionClosedException;
import org.apache.commons.net.ftp.FTPReply;


public class Fdb {
   public static final String USAGE =
      "Usage: Fdb <local file>\n" +
      "\nUploads local file to remote ftp servers in binary transfer mode.\n";

   public static void main(String[] args) {
      String[]    ftphost = { "filedb1.test", "filedb2.test"};
      FTPServer[] ftpsvr = new FTPServer[ftphost.length];
      File fl = null;
      FileInputStream is = null;

      if (args.length == 0) {
         System.out.println(USAGE);
         System.exit(-1);
      }

      try {
         fl = new File(args[0]);
         is = new FileInputStream(fl);
      } catch (Exception e) {
         System.exit(-1);
      }

      // data type initialization
      for (int i = 0; i < ftpsvr.length; ++i) {
         ftpsvr[i] = new FTPServer();
         ftpsvr[i].client = new FTPClient();
         ftpsvr[i].client.setConnectTimeout(1000); // one sec timeout
         try {
            ftpsvr[i].client.setSoTimeout(1000);
         } catch(Exception e) {}
         ftpsvr[i].client.addProtocolCommandListener(new PrintCommandListener(
                  new PrintWriter(System.out)));
         ftpsvr[i].hostname = ftphost[i];
      }

      // ftp connections
      for (int i = 0; i < ftpsvr.length; i++) {
         try {
            ftpsvr[i].client.connect(ftpsvr[i].hostname);

            if (FTPReply.isPositiveCompletion(ftpsvr[i].client.getReplyCode())) {
               System.out.println(ftpsvr[i].hostname + " ftp connection");
               ftpsvr[i].online = true;
               System.out.println(ftpsvr[i].hostname + " marked server online");
            } else {
               System.out.println(ftpsvr[i].hostname + " no ftp connection");
               System.out.println(ftpsvr[i].hostname + " marked server offline");
            }
         } catch (Exception e) {
            ftpsvr[i].online = false;
         }
      }

      // connection negotiation
      for (int i = 0; i < ftpsvr.length; i++) {
         if (ftpsvr[i].online) {
            ftpsvr[i].client.enterLocalPassiveMode();
            try {
               ftpsvr[i].client.login("ftp", "");
               ftpsvr[i].client.setFileType(FTPClient.BINARY_FILE_TYPE);
               ftpsvr[i].client.changeWorkingDirectory("/pub/incoming");

               // added random number for testing purposes
               ftpsvr[i].os = ftpsvr[i].client.storeFileStream((new Random()).nextInt(1000)
+ args[0]);
            } catch (java.io.IOException e) {
               ftpsvr[i].online = false;
            }
         }
      }

      // Writing input byte streams to ftp server destinations
      byte buf[] = new byte[8192];

      int bytesRead = 0;

      try {
         bytesRead = is.read(buf);
      } catch(Exception e) {}

      System.out.println("writing data");
      while (bytesRead != -1) {
         // write data out to ftp servers
         for (int i = 0; i < ftpsvr.length; i++) {
            try {
               if (ftpsvr[i].online) {
                  if (FTPReply.isPositivePreliminary(ftpsvr[i].client.getReplyCode())
                        && ftpsvr[i].os != null) {
                     System.out.print(".");
                     ftpsvr[i].os.write(buf, 0, bytesRead);
                  } else {
                     System.out.println("non - positive reply on " + ftpsvr[i].hostname);
                  }
               }
            } catch (Exception e1) {
               // here we're assuming any exception was generated by
               // an I/O fault related to writing to the ftp server,
               // thus the server is offline

               System.out.println("**FAULT writing to " + ftpsvr[i].hostname);
               ftpsvr[i].online = false;
            }
         }

         try {
            bytesRead = is.read(buf);
         } catch (Exception e) {}
      }

      System.out.println("done.");
      try {
         is.close();
      } catch (Exception e) {}

     for (int i = 0; i < ftpsvr.length; i++) {
        if (ftpsvr[i].online) {
           System.out.println("closing output stream " + ftpsvr[i].hostname);
           try {
              ftpsvr[i].os.close();
              ftpsvr[i].client.completePendingCommand();
              ftpsvr[i].client.logout();
              ftpsvr[i].client.disconnect();
           } catch (Exception e) {}
        }
     }
   }
}


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