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Functions

determine if tcp port is open

Terminal - determine if tcp port is open
nc -zw2 www.example.com 80 && echo open
2009-12-07 21:35:25
User: sputnick
Functions: echo
6
determine if tcp port is open

@putnamhill, no need if statement in that case.

&& is a AND and || is a OR

Alternatives

There is 1 alternative - vote for the best!

Terminal - Alternatives
lsof -i :22
nmap -p 80 hostname
2009-12-08 20:25:28
Tags: netcat nc
4

for udp

nmap -sU -p 80 hostname

if (nc -zw2 www.example.com 80); then echo open; fi
2009-12-07 20:04:55
User: putnamhill
Functions: echo
Tags: netcat nc
2

Requires netcat.

nc <ip> <port> -v
fuser -n tcp -s <port> && echo "+open"

Know a better way?

If you can do better, submit your command here.

What others think

@sputnick, thanks for the && tip. This came from a script of mine that includes an else clause. Does look much cleaner with the and construct.

Comment by putnamhill 242 weeks and 3 days ago

poor man's nmap...nice!

Comment by bubo 242 weeks and 1 day ago

nc is absolutely not a poor mans nmap. If anything, nmap is a wrapper for a watered down netcat.

Things netcat can do, which nmap cannot.

#1 Assist in hard drive cloning across the network.

#2 Be a telnet server

#3 Be a chat server

#4 Transfer files

#5 Be a web server

#6 Proxy dns requests

#7 Proxy ssh requests

...

Comment by Zhoul 91 weeks and 5 days ago

Your point of view

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