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56 lines
1.3 KiB
Markdown
56 lines
1.3 KiB
Markdown
# Netcat
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1. [TL;DR](#tldr)
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1. [Further readings](#further-readings)
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1. [Sources](#sources)
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## TL;DR
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Options of interest:
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- `-N`: close the network socket when finished; not available in nmap's netcat
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- `-l`: bind to the port and listen for incoming connections (server mode)
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- `-n`: do not resolve hostnames via DNS
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- `-p`: specify the source port to use
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- `-t`: use telnet negotiation
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- `-u`: use UDP
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- `-v`: set verbosity level; can be used several times
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- `-w=SECS`: timeout for connects and final net reads, in seconds
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- `-z`: zero-I/O mode, exit once connected
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```sh
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# Install
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dnf install 'nmap-ncat'
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yum install 'nmap-ncat'
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# Check ports on hosts.
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nc -Nnvz 192.168.0.81 22-25
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nc -Nvz host.name 443
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nc -Nvz -u dns.server 123
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# List hosts with a specific port open.
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# But you might just want to use `nmap`.
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parallel -j 0 "nc -Nnvz -w 2 192.168.0.{} 22 2>&1" ::: {2..254} \
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| grep -v "timed out"
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# Wait for a host to be up.
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until nc -Nvz -w 3 pi.lan 22; do sleep 3; done
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# Listen mode.
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nc -l 5666
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```
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## Further readings
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### Sources
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- [How To use Netcat to establish and test TCP and UDP connections]
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<!--
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Reference
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═╬═Time══
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-->
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<!-- Others -->
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[how to use netcat to establish and test tcp and udp connections]: https://www.digitalocean.com/community/tutorials/how-to-use-netcat-to-establish-and-test-tcp-and-udp-connections
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