[Edit]

Bash - how to scan open ports with netcat / nc in Debian Linux?

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Created by:

Khloe-Kaiser

578

Using Bash it is possible to scan open ports with netcat (nc command) in Debian family Linux in the following way.

Quick solution:

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#!/bin/bash
​
for (( i = 1; i < 65535; ++i ))
do
    nc -z -w 1 "127.0.0.1" "$i" < /dev/null;
    [ $? -eq 0 ] && echo "Open port $i";
done

Hints:

127.0.0.1 should be changed to the scanned computer IP address,
to install nc command got to the description in the last section.

Reusable script example

Edit

Simple steps:

1. create port_scanner.sh script file:

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#!/bin/bash
​
broken=0;
​
function break_script {
    broken=1;
}
​
trap break_script SIGINT;
​
for (( i = 1; i < 65535; ++i ))
do
    nc -z -w 1 "$1" "$i" < /dev/null;
    [ $? -eq 0 ] && echo "Open port $i";
    [ $broken -eq 1 ] && break;
done

2. assign permissions to execute the script with:

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chmod u+x port_scanner.sh

3. run port_scanner.sh script with the following command:

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./port_scanner.sh 127.0.0.1

Where:

127.0.0.1 should be changed to the scanned computer IP address.

Example output:

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Open port 22
Open port 80
Open port 111
Open port 3306
Open port 8005
Open port 8080

Note: click Ctrl+C to stop script.

Netcat installation

Edit

Use the following commands to install nc command:

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$ sudo apt-get update
$ sudo apt-get install netcat

Alternative titles

Bash - check open ports under Linux

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