Using Netcat: some practical commands

$ nc -l 2389

Also, we can use it to conectarnos to a port (2389), recently opened:

$ nc localhost 2389

Now if we write on the side of the also information, will arrive next to the server:

$ nc localhost 2389
HI, server

In the terminal where the server:

$ nc -l 2389
HI, server

We have seen an example of how to use nectar for client-server communication.

2.-Use Netcat to transfer files:

Netcat can be used to transfer files. On the side of also information Suppose we have a file called 'testfile' that contains:

$ cat testfile
hello testfile

and on the side of server we have an empty file called 'test'.

Now we side with the server:

$ nc -l 2389 > test

and we run the client as follows:

cat testfile | nc localhost 2389

When we check the 'test' file in the server:

$ cat test
Hello testfile

We have transferred data from also information al server.

3.-Netcat supports timeouts:

Sometimes when we open a connection we do not want it to remain open indefinitely, so to solve this problem we use the option -w, so that after x amount of seconds the connection between client-server is closed.

Server:

$nc -l 2389

Client:

$ nc -w 10 localhost 2389

The connection will be closed after 10 seconds.

Note: you should not use the option -w with the option -l on the side of server as -w it would have no effect and therefore the connection would remain open indefinitely.

4.-Netcat supports IPV6:

The options -4 y -6 force Netcat that uses the IPv4 or IPv6 protocol respectively.

employee:

$ nc -4 -l 2389

Client:

$ nc -4 localhost 2389

Now, if we run the command netstat, we would see:

$ netstat | grep 2389
tcp 0 0 localhost:2389 localhost:50851 ESTABLISHED
tcp 0 0 localhost:50851 localhost:2389 ESTABLISHED

The first parameter of the above output if it were IPv6 it would show a 6 after the tcp, but as we use IPv4 show us only tcp

.

Now, let's force Necati for it to use IPv6:

Server:

$nc -6 -l 2389

Client:

$ nc -6 localhost 2389

Running netstat again we would see:

$ netstat | grep 2389
tcp6 0 0 localhost:2389 localhost:33234 ESTABLISHED
tcp6 0 0 localhost:33234 localhost:2389 ESTABLISHED

We can see how the tcp is now accompanied by a 6, indicating the use of IPv6.

5.-Deactivate the reading by STDIN of Netcat:

This functionality is available through the option -d. In this example we do it on the client side:

Server:

$ nc -l 2389

Client:

$ nc -d localhost 2389
Hi

The Hi text will not be sent to the server since reading via STDIN has been disabled.

6.-Force Netcat to stay awake:

When we have the server running and the also information disconnects, the server also ends:

Server:

$ nc -l 2389

Client:

$ nc localhost 2389
^C

Server:

$ nc -l 2389
$

We could see in the previous example that if the also information closes the connection also the server So what can we do? Our solution is to use the option -k, which forces the server to keep running.

Server:

$ nc -k -l 2389

Client:

$ nc localhost 2389
C^

Server:

$ nc -k -l 2389

We have seen that server keep running even though also information has been disconnected, thanks to the option -k that we add to the server.

7.-Configure Netcat to stay awake after an EOF:

Netcat is configured so that after receiving a EOF(End Of File) terminate the connection, normally this is what happens, but we can modify this default behavior of Netcat adding option -q. This option instructs Netcat It must wait x number of seconds before closing the connection.

Client:

El also information should be started as follows:

nc -q 5 localhost 2389

Now whenever the also information receives an EOF will wait 5 seconds before closing the connection.

8.-Use Netcat over UDP:

Default Netcat uses the protocol for its communication TCP, but we can also use UDP by option -u.

Server:

$ nc -4 -u -l 2389

Client:

$ nc -4 -u localhost 2389

Now also information y server are using the protocol UDP for your communication, we can check this through the command netstat.

$ netstat | grep 2389
udp 0 0 localhost:42634 localhost:2389 ESTABLISHED

Well, during the post we have seen some examples of the use of Netcat, they could appreciate that it is a very versatile tool, hence the hacker's Swiss army knife

, here we present just some of its functionalities, as always if you want more information: man nc, and they will see everything that can be done with this tool. Until the next post and Happy Hacking !!!

Article taken from humans.