TIL: Checking Port Connections on Servers

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nc is a great tool to check the port connection to a remote server. It is similar to telnet.

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-v: verbose
-z: Scan for listening daemons, do not send any data
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> nc -vz 10.xxx.xxx.xxx 1221
found 0 associations
found 1 connections:
     1: flags=82<CONNECTED,PREFERRED>
 outif en0
 src 192.168.xxx.xxx port 5333
 dst 10.xxx.xxx.xx0 port 1221
 rank info not available
 TCP aux info available
Connection to 10.xxx.xxx.xxx port 1221 [tcp/afs3-prserver] succeeded!