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Simple tcp server using netcat
#!/bin/bash
# Simple tcp server using netcat
# - depending on the netcat version either use nc -l 5555 or nc -l -p 5555
# - verify with `telnet locahhost 5555`
# - quit the telnet with `ctrl-]` and then type quit
# - the while loop is there so reopen the port after a client has disconnected
# - supports only one client at a time
PORT=5555;
while :; do nc -l -p $PORT | tee output.log; sleep 1; done
@r3duc3
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r3duc3 commented Jan 20, 2021

how to create tcp server like this and public can connect to spesific address?

@phuesler
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phuesler commented Jan 20, 2021

You have to listen on 0.0.0.0. Depending on your netcat version you can do -l 0.0.0.0. Then your computer needs to be reachable from the internet either through a public ip address or NAT settings on your firewall/router. If it is from within the LAN, then this work if your local firewall allows it.

On my mac this works:

nc -l 0.0.0.0 5555

@r3duc3
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r3duc3 commented Jan 20, 2021

emm how?😅

@phuesler
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What are you trying to achieve?

@r3duc3
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r3duc3 commented Jan 21, 2021

I tried to create tcp server, the command is nc -lvp 9999 and this is the output

Ncat: Version 7.91 ( https://nmap.org/ncat )
Ncat: Listening on :::9999
Ncat: Listening on 0.0.0.0:9999

and only in local can connect to that server, and I want public can connect too but how?

@phuesler
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  • Is the server accessible by another computer within the same network?

@r3duc3
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r3duc3 commented Jan 21, 2021

emm... I dont know

@phuesler
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phuesler commented Jan 21, 2021

What is the server supposed to do? Deliver a website?

@r3duc3
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r3duc3 commented Jan 21, 2021

I want the server accept connection from outside(global), not only from inside(localhost)

@phuesler
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phuesler commented Jan 21, 2021

Do you have access to your internet router? Am I assuming correctly you are running this on your computer at home and not on a server?

@phuesler
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I don't understand the question. What is your web? And what is the TCP server supposed to do?

@r3duc3
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r3duc3 commented Jan 23, 2021

ugh sorry, my question ends here. Thanks for your response

@Tuanm
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Tuanm commented Dec 5, 2022

I want the server accept connection from outside(global), not only from inside(localhost)

I guess you've already found out the solution.

For guys who come here later, you have to run this script on a public machine (having a public IP address) to make it accessible globally. Of course, the port on which nc is listening must be open as well (using ufw).

@phuesler
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phuesler commented Dec 6, 2022

If that isn't the case, you can use a service like ngrok to make that port publicly available.

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