Is it possible to do it in one netcat invocation?
This works:
nc WHKWDCTGABUZUN1 12345 -w 5
How do I make this work?
nc WHKWDCTGABUZUN1,WHKWDCTGABUZUN2,WHKWDCTGABUZUN3 12345 -w 5
As far as I know, nc cannot directly do what you want. But, as the man pages say, nc works nicely in scripts, so you can do something like:
#!/bin/bash
ADDRESSES=("WHKWDCTGABUZUN1" "WHKWDCTGABUZUN2" "WHKWDCTGABUZUN3")
for ADDR in ${ADDRESSES[#]}
do
nc "$ADDR" 12345 -w 5
done
You can wrap this into a shell script that will send whatever you pass on stdin to each of the hosts.
If this doesn't work for you, check out one or more of the beefed-up versions of nc, including ncat and socat, both of which are available for Linux. I'm not sure that they can do what you want either, but it's more likely.
You can't actually do that in a single line, the way you're asking. However, something like this may work:
printf "WHKWDCTGABUZUN1\nWHKWDCTGABUZUN2\nWHKWDCTGABUZUN3\n" |
while read address; do
nc "$address" 80 -w 5 <<< GET;
done
Related
On RHEL 7.2 OS, I get following error when trying to run nc commnad
nc -z -v -w1 host port
nc: invalid option -- 'z'
Ncat: Try `--help' or man(1) ncat for more information, usage options and help. QUITTING.
Is there any alternative to it
maybe nc is a link to ncat, use the commands to checkļ¼
which nc | xargs ls -l
if the nc is linked to ncat,you should relink nc to netcat, if netcat is not installed, refer the website:http://netcat.sourceforge.net/download.php
It seems the old version of nc is being phased out everywhere in favour of Nmap Ncat. Unfortunately this doesn't have the rather useful -z option.
One way to get equivalent functionality (test whether the target host is listening on a given port) is to transform this:
nc -z hostname port
Into this:
cat /dev/null | nc hostname port
You might also want to add in an option like -w 1s to avoid the long default timeout.
There might be a cleaner combination of options that avoids the need for the /dev/null but I couldn't figure out what.
I've also seen talk of using tcping to do the same thing, but that doesn't seem to be available on all distros.
On the newer RHEL 7 nc is a link to ncat, while you may be used to nc on the older RHEL6 and below.
ncat seems not to have the -z option, and being a different project having a look at it's man page is a good idea, or at least examine it's internal help
ncat -h
I want command to get Linux machine(amazon) external/public IP Address.
I tried hostname -I and other commands from blogs and stackoverflow like
ifconfig | sed -En 's/127.0.0.1//;s/.*inet (addr:)?(([0-9]*\.){3}[0-9]*).*/\2/p'
and many more. But they all are giving me internal IP Address.
Then I found some sites which provides API for this.
Example : curl http://ipecho.net/plain; echo
But I don't want to rely on third party website service. So, is there any command line tool available to get external IP Address?
simplest of all would be to do :
curl ifconfig.me
A cleaner output
ifconfig eth0 | awk '/inet / { print $2 }' | sed 's/addr://'
You could use this script
# !/bin/bash
#
echo 'Your external IP is: '
curl -4 icanhazip.com
But that is relying on a third party albeit a reliable one.
I don't know if you can get your external IP without asking someone/somesite i.e. some third party for it, but what do I know.
you can also just run:
curl -4 icanhazip.com
This is doing the same thing as a command the -4 is to get the output in Ipv4
You can use this command to get public ip and private ip(second line is private ip; third line is public ip.)
ip addr | awk '/inet / {sub(/\/.*/, "", $2); print $2}'
I would suggest you to use the command external-ip (sudo apt-get install miniupnpc) as it (I'm almost sure) uses upnp protocol to ask the router instead of asking an external website so it should be faster, but of course the router has to have upnp enabled.
You can simply do this :
curl https://ipinfo.io/ip
It might not work on amazon because you might be using NAT or something for the server to access the rest of the world (and for you to ssh into it also). If you are unable to ssh into the ip that is listed in ifconfig then you are either in a different network or dont have ssh enabled.
This is the best I can do (only relies on my ISP):
ISP=`traceroute -M 2 -m 2 -n -q 1 8.8.8.8 | grep -m 1 -Eo '[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}'`
extIP=`ping -R -c 1 -t 1 -s 1 -n $ISP | grep RR | grep -m 1 -Eo '[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}'`
echo $extIP
Or, the functionally same thing on one line:
ISP=`traceroute -M 2 -m 2 -n -q 1 8.8.8.8 | grep -m 1 -Eo '[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}'` | ping -R -c 1 -t 1 -s 1 -n $ISP | grep RR | grep -m 1 -Eo '[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}'
to save it to a temporary & hidden file add > .extIP to the end of the last line, then cat .extIP to see it.
If your ISP's address never changes (honestly i'm not sure if it would or not), then you could fetch it once, and then replace $ISP in line two with it
This has been tested on a mac with wonderful success.
the only adjustment on linux that I've found so far is the traceroute "-M" flag might need to be "-f" instead
and it relies heavily on the ping's "-R" flag, which tells it to send back the "Record Route" information, which isn't always supported by the host. But it's worth a try!
the only other way to do this without relying on any external servers is to get it from curl'ing your modem's status page... I've done this successfully with our frontier DSL modem, but it's dirty, slow, unreliable, and requires hard-coding your modem's password.
Here's the "process" for that:
curl http://[user]:[password]#[modem's LAN address]/[status.html] | grep 'WanIPAddress =' | grep -m 1 -Eo '[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}'
That fetches the raw html, searches for any lines containing "WanIpAddress =" (change that so it's appropriate for your modem's results), and then narrows down those results to an IPv4 style address.
Hope that helps!
As others suggested, we have to rely on third party service which I don't feel safe using it. So, I have found Amazon API on this answer :
$ curl http://169.254.169.254/latest/meta-data/public-ipv4
54.232.200.77
For more details, https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-instance-metadata.html#instancedata-data-retrieval
The super-easy way is using the glances tool. you can install it on Ubuntu using:
$ sudo apt install glances
then using it with:
$ glances
and at the top of the terminal, it highlights your public IP address, and so many other information about your system (like what htop does) and network status.
For a formatted output use :-
dig TXT +short o-o.myaddr.l.google.com #ns1.google.com
it'll give you formatted output like this
"30.60.10.11"
also FYI,
dig is more faster than curl and wget
The following works as long as you have ifconfig and curl.
curl ifconfig.me
Running in bash under Ubuntu:
I have a source that generates me some output, but not straight away. Let's assume it is a first netcat listening on a socket: netcat -l 12345.
And I would like to pipe it to an outgoing netcat (connecting over TCP), e.g. netcat -l 12345 | netcat localhost 54321. But the tricky bit is, that I know there is nothing listening for that incoming connection on localhost 54321 when I run the command, but I know there will be one when the first actual character arrives through the pipe.
So my question is: is there a way either:
to delay the execution of the outgoing netcat until the first character arrives into the pipe, or
to delay the outgoing netcat from trying to establish the TCP connection until it receives the first character on its standard input? (no straight option for that in man, switching to UDP is not acceptable)
Thanks in advance!
Edit: In reality, the source is more complex than a netcat, namely it is a listening netcat piped through all sort of stream modification.
Using the research you already did and that I commented to (by not knowing it was an answer to your own question), here is the full delayed_netcat.sh:
#!/bin/bash
read line
netcat "${#}" < <(echo $line ; cat)
This first waits for a line of input and later prepends that line using a simple echo to the "newly generated" input to the actual netcat. The rest of stdin is just redirected using cat which slurps it from stdin and adds it to the input of netcat. It also supports passing commandline options and arguments to the "real" netcat.
The usage is as follows:
netcat -l 12345 | cmd1 | cmd2 | ... | ./delayed_netcat.sh localhost 54321
The netcat is delayed till the first line is read. If you really want to start it after the first character is read the parts with read and echo need some rewrite.
Port Forwarding or Port Mapping with netcat:
ncat -l -p 12345 -c 'ncat localhost 54321'
Using socat:
socat TCP4-LISTEN:12345 TCP4:localhost:54321
This command exits after the first connection is done.
I have found an answer to my question, but it is awful... so still looking for something better.
netcat -l 12345 | gawk '(NR==1){print""}{print;fflush()}' | ./delayed_netcat.sh
where ./delayed_netcat.sh:
#!/bin/sh
read line
netcat localhost 12345
So the read line delays the netcat localhost 12345 by waiting for and consuming the first input line, and I use gawk '(NR==1){print""}{print;fflush()}' to insert an empty line just before the first record... I'm sure there is room for much improvement to that!
I'm creating a TCP/IP interface to a serial device on a redhat linux machine. netcat in a bash script was used to accomplish this with out to much trouble.
nc -l $PORT < $TTYDEVICE > $TTYDEVICE
The problem is that the serial device uses carriage returns('\r') for line ends in its responses. I want to translate this to ("\r\n") so windows machines telneting in can view the response without any trouble. I'm trying to figure out how to go about this with a simple bash solution. I also have access to stty to configure the serial device, but there is no "\r" to "\r\n" translate on the input side(from what I can tell).
I did try to use tr on the input side of netcat, but it didn't work.
#cat $TTYDEVICE | tr '\r' '\r\n' | nc -l $PORT > $TTYDEVICE
Any ideas?
Your problem is that the client that connects to $PORT probably does not have a clue that it is working with a tty on the other side, so you will experience issues with tty-specific "features", such as ^C/^D/etc. and CRLF.
That is why
socat tcp-listen:1234 - | hexdump -C
telnet localhost 1234
[enter text]
will show CRLFs, while
ssh -t localhost "hexdump -C"
[enter text]
yields pure LFs. Subsequently, you would e.g. need
ssh -t whateverhost "screen $TTYDEVICE"
tl;dr: netcat won't do it.
This is overly difficult with standard tools, but pretty easy in perl (although perl is pretty much a standard tool these days):
perl -pe 's/\r/\r\n/g'
The version above will likely read the entire input into memory before doing any processing (it will read until it finds '\n', which will be the entire input if the input does not contain '\n'), so you might prefer:
perl -015 -pe '$\="\n"'
There are a number of versions of netcat (GNU and BSD) but you might want to try:
-C Send CRLF as line-ending
Is there a way to quickly bind to a TCP port/ip address and simply print out all information to STDOUT? I have a simple debugging solution which writes things to 127.0.0.1:4444 and I'd like to be able to simply bind up a port from bash and print everything that comes across. Is there an easy way to do this?
$ nc -k -l 4444 > filename.out
see nc(1)
Just because you asked how to do it in bash, though netcat answer is very valid:
$ exec 3<>/dev/tcp/127.0.0.1/4444
$ cat <&3
That is working as you expecting:
nc -k -l 4444 |bash
and then you
echo "ls" >/dev/tcp/127.0.0.1/4444
then you see the listing performed by bash.
[A Brief Security Warning]
Of course if you leave a thing like this running on your computer, you have a wide open gateway for all kinds of attacks because commands can be sent from any user account on any host in your network. This implements no security (authentication, identification) whatsoever and sends all transmitted commands unencrypted over the network, so it can very easily be abused.
Adding an answer using ncat that #Freedom_Ben alluded to:
ncat -k -l 127.0.0.1 4444
and explanation of options from man ncat:
-k, --keep-open Accept multiple connections in listen mode
-l, --listen Bind and listen for incoming connections