Server to server file transfer port? - linux

Question

I use a bash script(https://github.com/johnnywoof/FTP-Bash-Backup) to Backup my Debian www directory to a ftp server. everything went well but transfer blocked by firewall. The script using separate port every time so i can't unblock by Firewall. is there any way to specify a port ?
The Bash script
# FTP server settings
USERNAME=""
PASSWORD=""
SERVER=""
PORT=21
BACKUPDIR="/"
ndays=7
LOCAL_DIRECTORY="/home"
TEMP_BACKUP_STORE="/tmp"
ENCRYPT_BACKUP=false
AES_PASSWORD_FILE=""
timestamp=$(date --iso)
backup_remote_file_name="$timestamp.tar.gz"
backup_file="$TEMP_BACKUP_STORE/$backup_remote_file_name"
MM=`date --date="$ndays days ago" +%b`
DD=`date --date="$ndays days ago" +%d`
echo "Removing files older than $MM $DD"
listing=`ftp -i -n $SERVER $PORT <<EOMYF
user $USERNAME $PASSWORD
binary
cd $BACKUPDIR
ls
quit
EOMYF`
lista=( $listing )
for ((FNO=0; FNO<${#lista[#]}; FNO+=9));do
# month (element 5), day (element 6) and filename (element 8)
#echo Date ${lista[`expr $FNO+5`]} ${lista[`expr $FNO+6`]} File: ${lista[`expr $FNO+8`]}
if [ ${lista[`expr $FNO+5`]}=$MM ];
then
if [[ ${lista[`expr $FNO+6`]} -lt $DD ]];
then
echo "Removing ${lista[`expr $FNO+8`]}"
ftp -i -n $SERVER $PORT <<EOMYF2
user $USERNAME $PASSWORD
binary
cd $BACKUPDIR
delete ${lista[`expr $FNO+8`]}
quit
EOMYF2
fi
fi
done
echo "Creating backup..."
tar -czf $backup_file $LOCAL_DIRECTORY
if [ "$ENCRYPT_BACKUP" == "true" ]
then
echo "Encrypting backup using OpenSSL..."
output_encrypted_file="$backup_file.enc"
openssl enc -aes-256-cbc -salt -in $backup_file -out $output_encrypted_file -pass file:$AES_PASSWORD_FILE
rm $backup_file
backup_file=$output_encrypted_file
fi
echo "Uploading backup $backup_file ..."
ftp -n -i $SERVER $PORT <<EOF
user $USERNAME $PASSWORD
cd $BACKUPDIR
put $backup_file $backup_remote_file_name
quit
EOF
echo "Deleting temporary files..."
rm $backup_file
echo "Backup complete."

Answer 1

Switch to passive mode:
Insert passive in a new line after user command.
See: Active FTP vs. Passive FTP, a Definitive Explanation