How to implement a port scanner using some scripting language?
We can use any scripting language like python,perl,php etc. to achieve this. The idea is to create a socket on a port range and try to connect it. If connection allowed, means that particular port is open. If not, means the port is closed. Below is a nodeJS version of a port scanner trying to scan ports from number 1 to 10000.
(function() {
var net = require('net');
// the machine to scan
var host = 'localhost';
// starting from port number
var start = 1;
// to port number
var end = 10000;
// sockets should timeout asap to ensure no resources are wasted
// but too low a timeout value increases the likelyhood of missing open sockets, so be careful
var timeout = 2000;
// the port scanning loop
while (start <= end) {
// it is always good to give meaningful names to your variables
// since the context is changing, we use <code>port</code> to refer to current port to scan
var port = start;
// we create an anonynous function, pass the current port, and operate on it
// the reason we encapsulate the socket creation process is because we want to preseve the value of <code>port</code> for the callbacks
(function(port) {
// console.log('CHECK: ' + port);
var s = new net.Socket();
s.setTimeout(timeout, function() { s.destroy(); });
s.connect(port, host, function() {
console.log('OPEN: ' + port);
// we don't destroy the socket cos we want to listen to data event
// the socket will self-destruct in 2 secs cos of the timeout we set, so no worries
});
// if any data is written to the client on connection, show it
s.on('data', function(data) {
console.log(port +': '+ data);
s.destroy();
});
s.on('error', function(e) {
// silently catch all errors - assume the port is closed
s.destroy();
});
})(port);
start++;
}
})();
Install node.js from node website here . Save the above code in a js file and run the above from command prompt using
node
Below is a sample output of the above script:
OPEN: 445
OPEN: 443
OPEN: 1026
OPEN: 1027
OPEN: 1031
OPEN: 1025
OPEN: 1032
OPEN: 1034
OPEN: 1338
OPEN: 1339
OPEN: 2701
2701: ” ? S T A R T _ H A N D S H A K E
OPEN: 3389
OPEN: 5357
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