Netcat is a computer networking service for reading from and writing network connections using TCP or UDP

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23
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2answers
18k views

/dev/tcp listen instead of nc listen

With a netcat listener like: nc -l <port> < ~/.bashrc I can grab my .bashrc on a new machine (doesn't have nc or LDAP) with: cat < /dev/tcp/<ip>/<port> > ~/.bashrc My ...
18
votes
3answers
34k views

convert a hex string to binary and send with netcat

I have a binary file that I can send with netcat: $ nc -l localhost 8181 < my.dat The file contains this: $ xxd my.dat 0000000: 0006 3030 3030 4e43 ..0000NC What I really ...
12
votes
1answer
8k views

Remote desktop over SSH reverse tunnel to replace TeamViewer

I want to open a remote desktop session from my laptop to desktop over my SSH (reverse) tunnel. That should be simple (or at least doable), right? Until now I've been using Team Viewer to log in to ...
11
votes
3answers
10k views

Using in/out named pipes for a TCP connection

I've been fiddling with getting this to work for a while now, so I suspect some sort of fundamental misunderstanding about how pipes work is the root cause of my troubles. My goal is to initiate a ...
8
votes
4answers
2k views

Simplest way to send files over network

What is the simplest and most versatile way to send files over the network to other computers? By that I mean computers that other people are using at the moment. I don't think SSH works if the ...
7
votes
3answers
6k views

How does netcat know if a UDP port is open?

So I can use this netcat command to check if a UDP port is open: $ nc -vz -u 10.1.0.100 53 Connection to 10.1.0.100 53 port [udp/domain] succeeded! Unlike TCP, UDP is connectionless (fire and ...
7
votes
3answers
12k views

Test if telnet port is active within a shell script

I am trying to create a script to test whether it is possible to login via telnet. I do not want to really log in; therefore, expect is not needed. I just want to see if I am able to get a login ...
7
votes
7answers
2k views

How to grep netcat output

I'm trying to grep live text stream from netcat, but it doesn't work for me: netcat localhost 9090 | grep sender returns nothing, but I'm sure that it should. If I redirect the netcat output to a ...
6
votes
2answers
6k views

Howto create a permanent client connection with netcat?

I'm writing a bash script that constantly read a folder in a loop to send data to a server at a defined time interval. I'm using netcat as the tool to connect to the server and send the data. My ...
5
votes
2answers
13k views

How to make netcat use an existing HTTP proxy

I can access a web page just fine by directly hitting my web server as follows: $ echo "GET /sample" | nc web-server 80 This is contents of /sample... $ Now, I would like netcat to go via a Squid ...
5
votes
2answers
1k views

is it possible to send the remote connector ip via netcat?

Actually I want to make something like ifconfig.me functionality but only for my internal network. I see it the way smth on server listens some port and send ip of connected remote machine. Seems nc ...
5
votes
1answer
7k views

netcat in shell script giving invalid connection

I have a shell script that uses netcat to listen to localhost on port 1111 for web requests. Every time I try accessing localhost:1111/index.html for example I get: invalid connection to [127.0.0.1] ...
4
votes
2answers
16k views

nc: bind failed: Address already in use

I am trying to execute nc command from a script , my script is executing nc command on different ports of Destination using the same source port. e.g: nc -p 8140 -z -v -n 10.X.X.9 9090 nc -p 8140 -z ...
4
votes
2answers
5k views

SSH jumping over socks(4/5) proxy chain. Host -> socks proxy -> socks proxy -> destination

I got a great answer for my previous question about connecting from Machine A to Machine C via Socks proxy located on Machine B. Say Machine B Ip is 218.62.97.105 and it is listening on port 1080 ...
4
votes
2answers
805 views

Why does this shell snippet to check if hosts are up using netcat stop prematurely?

Q: Why does the second iteration exits after 10.175.192.16? Can someone explain that? Or I just found a "while/netcat" bug? a.txt's content: $ cat a.txt 10.175.192.14 10.175.192.16 10.175.192.17 $ ...
4
votes
0answers
279 views

Remote Mouse netcat (/dev/input/mice)

I was playing around with nc and I'm discovering how powerful and versatile this tool is. I was wondering how the file /dev/input/mice works because when I do cat /dev/input/mice you see the output, ...
3
votes
3answers
2k views

How can I read lines at a fixed speed?

I need to read a large log file and send it over a local network using (netbsd) netcat between two VMs on the same host workstation. I know that netcat has an interval, but as far as I can tell, the ...
3
votes
1answer
3k views

Netcat (nc6) - Minimal IPv6 only TCP Server and Client

Im am trying to set up a basic IPv6 only echo-server using netcat (or rather nc6). Client and server are both in the same local network. However, the client quits immediately: IPv6-Server: $ nc6 -...
3
votes
1answer
2k views

cat file to udp, pt 2: send 1 udp packet per ^C-delimited line

Yesterday I asked a question about catting a file over a UDP socket in bash. The solution we came up was netcat -c -w 1 -v -u -s 127.0.0.1 239.255.0.1 30001 < test.txt. This worked in the sense ...
3
votes
2answers
927 views

Different redirection styles with netcat and tee giving different results

In trying to trace a simple HTTP GET request and its response with nc, I'm running into something strange. This, for example, works fine: the in file ends up containing the HTTP GET request and the ...
3
votes
1answer
809 views

nc -l in background closes immediately (nc -l 1234 &)

When I put this nc -l 12345 >nc_out in a shell script, run it and then connect from other shell using telnet, it allows me to type some text and have it end up in nc_out. But if I start nc in ...
3
votes
3answers
68 views

how to get espeak to continuously speak stdout piped from netcat

I have a Raspberry pi 3 that I want to use as a sort of PA system, using espeak to announce stuff piped from netcat, which is getting input from a remote server. On the pi, I initiate the listener ...
3
votes
1answer
67 views

How can I repeatedly send the contents of a file via socat / ncat to a socket

I'm running some performance testing, and I'm trying to send the same file repeatedly to a socket. If I do something like: $ socat -b1048576 -u OPEN:/dev/zero TCP4-LISTEN:9899,reuseaddr,fork $ ...
3
votes
3answers
2k views

netcat doesn't work as expected when detached from console with nohup (Ubuntu/Debian 64bit)

I'm trying to leave netcat running and close the ssh session (even stop the ssh daemon). But it then exits before all of the data is written. I'm testing in a non-ssh (local) console: nohup nc -l -p ...
3
votes
1answer
5k views

Stream Video using Netcat and VLC

I'm trying to use netcat on Linux server to stream video to my windows client using VLC I started running netcat on Linux: cat /media/HD1/myMovie.mkv | nc -l 8668 In VLC Windows Client I tried to:...
2
votes
1answer
373 views

How to avoid sending EOF from a script parsing requests from and sending answers to netcat

I made a simple server using netcat and backpipe: mkfifo backpipe nc -l 8080 < backpipe | parseRequests.sh > backpipe The contents of "parseRequests.sh" is just: #!/bin/sh if [ "$1" = "1+1" ]...
2
votes
2answers
55 views

Output of one command is piped to another one; how to close both?

I call Qt Assistant like suggested on stackoverflow: nc -lkU ~/.assistantfifo | assistant -enableRemoteControl & Qt Assistant window is opened, and if I call jobs, it returns: [1] + running ...
2
votes
3answers
575 views

Servers running from chrooted Ubuntu on HP TouchPad? [closed]

The problem: servers appear to be broken inside my Ubuntu chroot. No matter what kind of server I try to run, they all seem unresponsive (VLC server won't respond to client, mkRemote doesn't move the ...
2
votes
1answer
175 views

How to pipe a sample log message manually to logstash for processing

I have set-up an ELK server in testing environment. I intend to send log messages from different clients to ELK, but first i want to test it from localhost to verify it running properly. Previously ...
2
votes
2answers
184 views

How to write to a file with netcat? And set it to grow to a certain size and begin overwriting itself?

I'm currently writing a program that prints to a Zebra printer. Because my office doesn't have a zebra printer, we print to a linux VM running netcat with nc -k -l -p 9100 | tee labels.txt so that we ...
2
votes
1answer
6k views

How to put value of echo pipe netcat commands into variable [duplicate]

I have this command succession: echo -ne "/dev/shm/test.sh" | netcat 89.196.167.2 4567 and let's say it return a string like, for example "Hello...bla". (on the 89.196.167.2 i have made a server ...
2
votes
1answer
75 views

How could I EOF `cat` through `netcat` without closing connection?

I have run into a problem where I have a ncat server with the command ncat -l [port] -k -c "cat > foo; cat > bar". When I connect to this server through netcat, it allows me to write to the file ...
2
votes
1answer
305 views

Jumping ssh hosts without netcat

I have access to an intermediate server to which I can connect with ssh. From there I can connect to other servers: A→B→C, where A is my laptop, B is an intermediate server accepting connections from ...
2
votes
1answer
143 views

Log from TCP Port breaking messages on characters other than newline

I'm working on a set of scripts to monitor some external services that log to a TCP port. function handleMessage { while read message do # Handle $message done } nc -d $ipadd $port | ...
2
votes
2answers
1k views

How to copy a partition over network

I want to copy a Windows 7 partition that came installed on my laptop to my desktop computer. I've tried: # bzip2 -c /dev/sda5 | nc 192.168.1.1 2222 # on laptop # nc -l 2222 | bzip2 -d > /dev/...
2
votes
1answer
45 views

tunnel netcat video streams to mplayer

I am sending a video stream over my network and I want to encrypt it with ssh. This solution below works: on machine 1 I run ./capture | nc 192.168.1.65 5001 on machine 2 I run netcat -l -p 5001 |...
2
votes
0answers
205 views

named pipe proxy over SSH

I am used to forwarding a remote service port on localhost using ssh like: ssh -L 2181:localhost:2182 user@server (forward remote host port 2182 to local port 2181) now, from the machine I ssh to, I ...
2
votes
0answers
49 views

How to make netcat print colourful text?

on my Mac I have an peripheral that sends text data to localhost:2332. Some of them are coloured, like this: "\e[1;31mRed text here\e[m normal text here", I use nc loacal host to monitor the data ...
1
vote
2answers
290 views

netcat to capture ethernet

How can I make sure the result of the following command: nc eth0 &> capture.txt would capture the data + errors transmitted via eth0?
1
vote
1answer
495 views

grep not matching in nc output

I'm using nc to scan for open ports but I'm scanning a wide range and it's displaying too many results. Trying to grep it for the word "succeeded" doesn't work for some reason: $ nc -zv localhost ...
1
vote
1answer
185 views

Can't redirect cut output

When I try to redirect the output of cut it always seems to be empty. If don't redirect it, the output shows in terminal as expected. This is true for OS X 10.10 and Linux 4.1.6. This works: root@...
1
vote
2answers
84 views

Is there a netcat like utility that uses unix sockets?

netcat is wonderful, let me count the ways -- is to much let me sum up -- tcp/ip4, udp/ip4, tcp/ip6, udp/ip6, but what I need is stream/unix. I could write it in half a day, but If someone has already ...
1
vote
1answer
49 views

Can't pipe into netcat

I have a squid proxy running in a docker container, started like this: docker run --privileged -d --publish=3128:3128 --name foo squid I want to get some information from it, from another container ...
1
vote
1answer
112 views

How to have netcat server close after n seconds

I need to use nc in a weird way, where I want the server to first send a file, and then recieve a file, and this repeats. I would like to have every instance of the server server close after some ...
1
vote
2answers
155 views

How can I “man-in-the-middle” a specific port?

When I want to figure out how a certain protocol works (let's say in this case, the HTTP protocol on port 80), I open two terminal windows: nc -l 80 nc google.com 80 I then fire up the program I ...
1
vote
1answer
485 views

NetCat ignoring (not sending) network data to broadcast addresses

If I run these NetCat below commands (no error messages at all) during a WireShark capture running (capture filter= udp dst port 4000) : luis@Zarzamoro:~$ echo "Hello" | nc -w1 -4u 255.255.255.255 ...
1
vote
1answer
69 views

Is there a way to have netcat listen and place incoming files in a destination directory?

I'd like to use netcat to regularly transfer files to a media server on my network. However, I can't figure out how (or if it's possible) to do something like nc -l 5959 > /media/data/, where ...
1
vote
1answer
519 views

What does the %h and %p do in this command?

$ ssh -o User=fred -o ProxyCommand="nc -X 5 -x localhost:9150 %h %p" server.example.org It's from http://en.wikibooks.org/wiki/OpenSSH/Cookbook/Proxies_and_Jump_Hosts I can't find any comments about ...
1
vote
1answer
34 views

netcat doesn't print response

I'm trying to send commands to a tcp port using netcat and pipe response when I run netcat and type my command it prints response correctly but when I pass command from a pipe it sends the command ...
1
vote
1answer
77 views

Empty response on HTTP request with netcat

Testing a simple HTTP request using nc: $ printf 'GET / HTTP/1.1\r\nHost: mozilla.org\r\nAccept: */*\r\n\r\n' | nc mozilla.org 80 HTTP/1.1 301 Moved Permanently Content-Type: text/html Date: Thu, 10 ...