How to change a Unix ftp port number

Here's how you change the port on which FTP is serviced on a SCO Unix machine:

 

Configuration:

 

1.  Open the /etc/services file with a text editor and modify the following entries:

 

    ftp-data        20/tcp
    ftp               21/tcp
 

20 and 21 are the port numbers respectively that need to be changed to new values.  You can edit the values to:

 

    ftp-data        65120/tcp
    ftp               65121/tcp
 

This will change the port on which FTP is serviced to 65121 (the second entry).   The first entry (ftp-data), will automatically sent to the client from the server.

 

2.  Restart the "inetd" daemon

 

Run the command:

   

    ps -ef | grep inetd

 

you will see a process entry for "inetd"

 

kill that process using:

 

    kill <pid> 

 

    where <pid> is the process id.

 

Now run the command:

 

    /etc/inetd

 

Then verify if the "inetd" process is running using the "ps" command above.

 

Invoking FTP to the server:

 

Once this change is made, you cannot open an ftp connection to the server using ftp in the command line directly to the server.  i.e.:

 

    ftp <server_name> 

 

will NOT work.

 

Instead you have to do the following:

 

   $ ftp

   ftp>  open <server_name>  65121

 

Note that the only port number you explicitly use will be that of the second (ftp) entry in /etc/services, not the first (ftp-data) entry.  However, you do need to change both entries.