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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 are 2 alternatives - 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 290 weeks ago

poor man's nmap...nice!

Comment by bubo 289 weeks and 6 days 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 139 weeks and 2 days ago

Your point of view

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