netcat - How do I synchronize my portscan and port listen scripts and how do i export all output to a .txt file? - bash

Question

My goal is to have a port listen script on Host A which listens on predefined ports using netcat.
While this script listens, the port scan script is running on Host B and checks if the ports on Host A or open or not.
The output of the scan script needs to be directed to a separate .txt file and must include all information from the nc -zvv output.
The listen script looks like this:
#!/bin/bash
# Define the four arrays of ports to listen on
ports_1st=(20 21 22 80 443)
ports_2nd=(2000 2001 2002 2003)
ports_3rd=(3000 3001 3002 3003)
ports_4th=(4000 4001 4002 4003)
# Sleep to allow the scan script to start and bind to all ports
echo "Start PortScan.sh as soon as port listen starts!"
sleep 5
echo -e "\n"
echo -e "\n"
# Countdown timer
echo "Start the port scan in:"
for i in 5 4 3 2 1; do
echo "$i..."
sleep 1
done
# Loop through each array of ports and use nc to listen on each port
echo "Listening on 1st ports..."
for ports in ports_1st; do
for port in "${!ports[#]}"; do
nc -l -k -p $port &
done
done
echo -e "\n"
echo "Listening on 1st ports completed"
echo -e "\n"
echo -e "\n"
echo "Listening on 2nd ports..."
for ports in ports_2nd; do
for port in "${!ports[#]}"; do
nc -l -k -p $port &
done
done
echo -e "\n"
echo "Listening on 2nd ports completed"
echo -e "\n"
echo -e "\n"
echo "Listening on 3rd ports..."
for ports in ports_3rd; do
for port in "${!ports[#]}"; do
nc -l -k -p $port &
done
done
echo -e "\n"
echo "Listening on 3rd ports completed"
echo -e "\n"
echo -e "\n"
echo "Listening on 4th ports..."
for ports in ports_4th; do
for port in "${!ports[#]}"; do
nc -l -k -p $port &
done
done
echo -e "\n"
echo "Listening on 4th ports completed"
echo -e "\n"
echo -e "\n"
# Wait for all background nc processes to complete
wait
echo "Portscan has been completed"
echo -e "\n"
echo -e "\n"
And the scanscript looks like this:
#!/bin/bash
# Define the range of ports to scan
ports_1st=(20 21 22 80 443)
ports_2nd=(2000 2001 2002 2003)
ports_3rd=(3000 3001 3002 3003)
ports_4th=(4000 4001 4002 4003)
# Define the IP of the target host
echo "Please enter the server IP of the target host!"
read target_host
echo -e "\n"
echo -e "\n"
# Define current date variable
current_date=$(date +"%Y-%m-%d")
# Loop through the range of ports and use nc to test for a response
echo "Scanning 1st ports..."
for ports in ports_1st; do
for port in "${ports[#]}"; do
nc -zvv -w 1 $target_host $port 2>&1 | tee -a Portscan_$current_date.txt
if [ $? -eq 0 ]; then
echo "Port $port is open" | tee -a Portscan_$current_date.txt
else
echo "Port $port is closed or connection timed out" | tee -a Portscan_$current_date.txt
fi
done
echo "1st port scan completed" | tee -a Portscan_$current_date.txt
echo -e "\n"
echo -e "\n"
echo "Scanning 2nd ports..."
for ports in ports_2nd; do
for port in "${ports[#]}"; do
nc -zvv -w 1 $target_host $port 2>&1 | tee -a Portscan_$current_date.txt
if [ $? -eq 0 ]; then
echo "Port $port is open" | tee -a Portscan_$current_date.txt
else
echo "Port $port is closed or connection timed out" | tee -a Portscan_$current_date.txt
fi
done
echo "2nd scan completed" | tee -a Portscan_$current_date.txt
echo -e "\n"
echo -e "\n"
echo "Scanning 3rd ports..."
for ports in ports_3rd; do
for port in "${ports[#]}"; do
nc -zvv -w 1 $target_host $port 2>&1 | tee -a Portscan_$current_date.txt
if [ $? -eq 0 ]; then
echo "Port $port is open" | tee -a Portscan_$current_date.txt
else
echo "Port $port is closed or connection timed out" | tee -a Portscan_$current_date.txt
fi
done
echo "3rd port scan completed" | tee -a Portscan_$current_date.txt
echo -e "\n"
echo -e "\n"
echo "Scanning 4th ports..."
for ports in ports_4th; do
for port in "${ports[#]}"; do
nc -zvv -w 1 $target_host $port 2>&1 | tee -a Portscan_$current_date.txt
if [ $? -eq 0 ]; then
echo "Port $port is open" | tee -a Portscan_$current_date.txt
else
echo "Port $port is closed or connection timed out" | tee -a Portscan_$current_date.txt
fi
done
echo "4th port scan completed" | tee -a Portscan_$current_date.txt
echo -e "\n"
echo -e "\n"
done
done
done
done
The problem is that the listen script seems to end instantly instead of waiting for all ports to be scanned and the portscan script does not put the proper output to the .txt file.
Do you have any ideas on how to fix this?
Side notes:
Netcat is mandatory to be used.
I am expecting to loop through each port mentioned in the listen script as well as in the scan script.
The scan script is supposed to prompt if the port is open or closed/timeout in a .txt file.