# nc
[](https://www.npmjs.com/package/nc)
[](https://david-dm.org/roccomuso/nc)
[](https://standardjs.com)
Porting Netcat in Node.js. CLI util. :computer:
To embed it in your Node.js app use the [netcat](https://github.com/roccomuso/netcat) package instead. This is meant to be used as a standalone tool, but it's not fully equal to the original implementation of netcat.
| Linux | Mac OS | Windows |
|-------|--------|---------|
| :white_check_mark: | :white_check_mark: | :white_check_mark: |
## What you can do
- [x] TCP & UDP
- [x] Backdoor (Reverse Shell)
- [x] Honeypot
- [x] File transfer
- [x] Port forwarding
- [ ] Proxy
- [x] Web Server & HTTP Client
- [x] Port scanning
## Install
$ npm install -g nc
## Usage
$ nc -l -p port [- options] [hostname] [port]
Available options:
```
-c shell commands as `-e’; use /bin/sh to exec [dangerous!!]
-e filename program to exec after connect [dangerous!!]
-b allow broadcasts
-h this cruft
-i secs delay interval for lines sent, ports scanned
-k set keepalive option on socket
-l listen mode, for inbound connects
-n numeric-only IP addresses, no DNS
-o file hex dump of traffic
-p port local port number
-r randomize local and remote ports
-s addr local source address
-u UDP mode
-U Listen or connect to a UNIX domain socket
-v verbose
-w secs timeout for connects and final net reads (client-side)
-z zero-I/O mode [used for scanning]
```
#### Server: Listen for inbound
$ nc -l -p 2389
#### Client mode
$ nc localhost 2389
Opening a raw connection to port `2389`.
#### Transfer file
| Server side | Client side |
|---------------------|------------------------------------|
| `nc -l 2389 > test` | cat testfile | nc localhost 2389 |
#### Timeout support
$ nc -w 10 localhost 2389
Connection above would be terminated after 10 seconds.
#### Force netcat server to stay up
$ nc -kl 2389
In this way the server remains up even if the client got disconnected.
#### Netcat execute
A far more exciting thing to do is to get a quick shell going on a remote machine by using the `-l` or `listen` option and the `-e` or `execute` option. When a connection is made, Netcat executes the program of your choice and connects the `stdin` and `stdout` of the program to the network connection.
$ nc -l -p 23 -e /bin/sh
#### Retrieve a website Homepage
Let's create a HTTP request file `get.txt` that contains the following line and then a blank
line:
```
GET / HTTP/1.0
```
To use Netcat to retrieve the home page of a web site use:
$ nc -v www.website.com 80 < get.txt
You will see Netcat make a connection to port 80, send the text contained in the file `get.txt`, and then output the web server's response to `stdout`.
#### Configure netcat client to retry on disconnect
In a normal scenario, if the nc client disconnect, it will not retry the connection.
With the `--retry ` or `-R ` param, it will retry the connection after tot seconds.
$ nc -R 5 localhost 2389
#### Unix socket file
If you have docker, let's try to list our containers' images connecting to the docker unix socket file:
```sh
$ echo -e "GET /images/json HTTP/1.0\r\n" | nc -U /var/run/docker.sock
```
PS. for this example root permissions are required: `sudo su`.
#### Netcat as a Proxy
```sh
$ mkfifo /tmp/fifo
$ nc -l -k -p 8080 /tmp/fifo
```
#### Netcat as a simple port scanner
$ nc -z 192.168.1.100 1-255
#### Dump hex traffic
If you use the `-o` option you can dump all hex traffic.
$ nc 127.0.0.1 4445 -o /tmp/log.txt
#### UDP Protocol
By default all the sockets that nc utility creates are TCP protocols but this utility also works with UDP protocol. To enable UDP protocol the -u flag is used.
| Server side | Client side |
|---------------------|------------------------------------|
| `nc -u -l -p 2389` | `nc -u localhost 2389` |
#### Send a UDP message
$ echo 'message' | nc -w 1 -u 192.168.1.111 514
Pipe via UDP (-u) with a wait time (-w) of 1 second to `192.168.1.111` on port `514`.
## DEBUG
Debug matches the verbose mode.
You can enable it with the `-v` param or the env var `DEBUG=nc`. This module uses the node implementation of [netcat](https://github.com/roccomuso/netcat) under the hood, to debug both use: `DEBUG=netcat:*,nc`.
## Author
Rocco Musolino ([@roccomuso](https://twitter.com/roccomuso))